The examination of a vast number of ticks, collected in late years from various hosts in many parts of the world, has resulted in the addition of several new species to the genus Haemaphysalis. Though only 13 of the species admitted by Neumann in his “Révision” (Pt. II, 1897) still stand, the number of recognised good species now reaches 43.

The new species herein described are of interest, although we can only deal with females, as is so frequently the case with this genus. One species (I. kempi), allied to the North American I. angustus, comes from a hitherto unexplored region on the north-east frontier of India, having been collected by the Abor Expedition. Two species (I. daveyi and I. oldi) are from Africa, and offer a peculiarity of structure in that they possess anal grooves having the form of a horse-shoe, an appearance only hitherto observed in three other species of Ixodes, all of which are African. The fourth species (I. ricinoides) is from China, and is allied to our I. ricinus:

Aragão (1912) has recently described a new species of tick which he raised through three complete generations upon cold-blooded animals, the natural hosts in Brazil. He gave the species the name Amblyomma agamum because reproduction occurred parthenogenetically, males not having as yet been observed. The tick, in common with most other Ixodidae, feeds upon three successive hosts in the larval, nymphal and adult stages; it may, however, undergo metamorphosis from larva to nymph upon the host. This observation of Aragão's is the first of the kind, for parthenogenesis has not hitherto been observed in ticks. In the course of his raising experiments he obtained thousands of females which laid fertile eggs in the absence of males.

During the course of the last few years our knowledge of parasitic worms in all their various relations has advanced and increased to a very considerable and satisfactory extent. From the purely zoological point of view the advances have been of the highest order, many important discoveries having been made, not only in connection with the morphology but also, and particularly, in connection with the development and bionomics of these worms. At the same time there has been a steadily increasing improvement in our ideas of their classification and relationships which has resulted in a much wider and more accurate conception of their zoological nature. While these rapidly accumulating discoveries have greatly extended the knowledge at our disposal, they have, in addition, rendered such facts easier of study and of use, with the result that the economic value of the subject as a whole has been very materially enhanced. Helminthology shares with Protozoology and Entomology the, in some respects, unenviable distinction of being of intrinsic importance not only to medicine, but also to veterinary and agricultural science. It has a smaller but no less definite economic importance in relation to fisheries. Apart from their purely zoological interest it is particularly as agents of disease that the parasitic worms are of importance, but there are a number of other matters connected with habits and distribution, on which a study of parasites may throw considerable light.

No group of ticks presents a more interesting biological study than the genus Dermacentor. The diversity of habits of these ticks is remarkable. These differences in habits, especially when we find them correlated with certain structural characteristics, would lead some to consider splitting the genus into two or more genera or subgenera. This we do not think well advised.

The following observations were made in September, 1908, during a short residence at Aberdeen where, through the kindness of Prof. J. Arthur Thomson, I was able to deal with a considerable number of fishes in the very limited time at my disposal1. The investigation was intended as a continuation of that already carried out at St Andrews, the object being to examine a number of fishes which could not readily be obtained at the latter place. There the fishes dealt with were mostly littoral forms, but at Aberdeen attention was mainly paid to the larger deep-water fish; of these a plentiful supply could be easily obtained. A few species were re-examined here.

In the course of our studies on species of Rhipicephalus, we have noted the great variability in size and structure observable in the genus. This variability has been a cause of much confusion in classification, as noted by Warburton (Parasitology, 1912, v. 1). It soon occurred to me, in seeking for an explanation of this variability, that it might well be due to nutrition, it being probable that, under natural conditions, a certain number of ticks are removed from the host before they have fed to repletion. When a host is infested with ticks it will brush or rub off a certain number prematurely and the ticks which are imperfectly fed would, doubtless, give rise to adults of small size. As stated, the great variability observed in Rhipicephalus is very striking. In the genus Ixodes, on the other hand, the size of the adults is fairly constant. In the latter case, we have, as a rule, to deal with small ticks provided in the immature stages with long hypostomes, both the small size and hypostomal structure rendering it most difficult for the tick to be removed prematurely from the host. It is difficult to remove Ixodes from the host without breaking the hypostome and using considerable force. In Haemaphysalis, as in Rhipicephalus, the immature stages are provided with short hypostomes and the ticks are more readily removed. The variation in size noted in adult Haemaphysalis, whilst considerable, is not as great as in Rhipicephalus, which would appear to be attributable to the smaller size of the tick, being in a measure a protection against its being prematurely removed from the host.

It has been pointed out by Warburton (1912) that the degree of variation within the species of the genus Rhipicephalus is very considerable, and in view of this fact it is important to investigate the range of a species and the value of the differential structural characters upon which species are based. The great majority of the Rhipicephali are inornate and this, in conjunction with the general lack of distinguishing structural features and the wide variation found within the species, renders determinations difficult. As Rhipicephalus pulchellus, however, possesses a characteristic and well-marked ornamentation, which is subject to but slight variation, any specimen, at least in the case of the males, may be determined without difficulty.