A standard nigrosin-eosin staining method in current use has been said to differentiate between live (unstained) and dead (stained) spermatozoa. In the present work, the method is applied to rabbit semen. The general results are comparable with those already obtained in the larger domestic animals. The effects of several technical and biological factors on staining capacity are evaluated, and the validity of the method is examined experimentally. Some statistical aspects are presented. The percentage of stained spermatozoa varies widely between rabbit males. To a large extent, any particular male preserves a characteristic percentage from one ejaculate to another. The percentage of stained spermatozoa is inversely related to the fertility of males as measured by the birth rate after natural mating.

Concurrently, an investigation was made of the incidence of a class of morphologically abnormal spermatozoa seen in the preparations. The classifications of spermatozoa by morphology and by staining capacity are highly correlated. For assessing semen quality, the morphological classification is considered to be as useful as the classification by staining capacity, and perhaps more useful.

Nigrosin-eosin staining of rabbit spermatozoa is discussed; firstly, in comparison with other animals and in relation to sources of variation; secondly, as a means of differentiating between live and dead spermatozoa; thirdly, as a means of assessing the fertility of semen; and fourthly, in relation to the alternative classification of spermatozoa by abnormal morphology.

In Meganyctiphanes the blood is pumped from the heart to the various regions of the body by way of a well-developed arterial system. It passes out of the open ends of the final sub-branches of the arteries into the various sinuses, finally collecting in the posterior ventral region of the thorax. From there, by the action of the pericardium and the muscles associated with the afferent branchial channels, it enters the afferent branchial channels whence it circulates through the branchial veins in the branchiæ, to the efferent branchial channels. The beating of the heart draws the blood into the pericardium whence it reaches the heart cavity by way of two pairs of ostia.

A gravity survey has been made of a glacier-dammed lake in Dronning Louise Land, North-East Greenland. Corrections for the effect of the local topography and the regional Bouguer anomaly are made to the values of the acceleration due to gravity measured at about 230 points on the lake and its shores. From the differences between the corrected values at the lake stations and those of the shores, depths of water under the lake stations are calculated, and a contour map of the lake bottom is drawn. A submerged shelf, 75 metres below the present lake level, persists around the western part of the lake. This may be the shore-line of a pre-glacial lake.

Triethylenemelamine induces chromosomal aberrations in Drosophila and in mammals. In the present paper the effects of intraperitoneal injections of the drug on the fertility of male mice are related to its mutagenic activity. Males were given prolonged or short treatment with the drug and were mated to females at frequent intervals.

Male fertility was greatly reduced after either treatment, a result similar to previous findings in the rat. Sterility for the first few weeks was due to dominant lethals causing embryonic mortality, and to oligospermia from 30 days after the injection. Embryonic mortality was reduced after lower doses, being maximal between 11 and 14 days after the injection, and little or no oligospermia resulted from this treatment.

The drug probably acted directly on spermatogenic cells; spermatids being most sensitive to the induction of lethals and spermatogonia to destruction; these estimates were based on the known rate of spermatogenesis in the mouse. The sensitivity of the stages of spermatogenesis and the translocation frequency induced by the drug have some similarities to the effects of X-rays on the testis.

The distribution of thiol (sulphydryl) groups in the wool follicle has been studied with Bennett's reagent; the strongest reaction was found immediately proximal to the prekeratinization (keratogenous) region. Mice and lambs were injected with cystine labelled with sulphur-35 and radioactivity was detected in the follicles, autoradiographically within a few minutes. A peak of activity formed in the follicle during the first few hours after injection which suggested that there is a rapid turnover of cystine in the body. But a small amount of activity could still be detected in the follicle up to at least 3 weeks afterwards.

Sulphur seems to enter the follicle immediately above the bulb, and reaches the fibre first on the side at which it is keratinized last. This method indicated the relative proportion of sulphur in different regions of the follicle and suggested that the sulphur becomes concentrated on keratinization. No difference in sulphur content was found between primary and secondary follicles, the ortho- and paracortex, and apparently between cortex and medulla. When labelled sulphate was injected, activity appeared first in the outer sheath, and only later in the fibre.