During my stay at the Plymouth Laboratory in 1931 I had an opportunity of investigating the innervation of the heart of Ligia oceanica, and of making some experiments on the function of the ganglionic trunk which constitutes the main element of its innervation. In a short note describing these experiments (Alexandrowicz, 1931) it was stated that a description of the arrangement of the nerve elements would appear in a short time. However, on later examination of the preparations it seemed to be desirable to verify some of the findings, but the same animal was no longer available. Another isopod, Mesidotea entomon, with which I tried to continue the work during my visit to the Marine Biological Laboratory in Hel, proved to be much less suitable for this kind of investigation despite its larger size. Later events, unfavourable for scientific work, caused the loss of all my preparations and a further delay. It is only now, thanks to the chance of working again at the Plymouth Laboratory, that I have been able to resume my investigations.