412 Proceedings of the 



IV. (1.) On the Genus Peltogaster (Rathke) ; an animal form parasitic 

 on the abdomen of crabs. (2.) On the occurrence of the Galathea An- 

 drewsii. By John Anderson, Esq. 



(1.) On the G-enus Peltogaster (Rathke}. 



My attention was first directed to this remarkable genus of 

 animals in the spring of 1855. Being then engaged in exa- 

 mining the different species of the Paguridce, in the Firth of 

 Forth, I was astonished to find attached to the left side of the 

 abdomen of a specimen of the Bernhardus a bright yellow- 

 coloured sac, resembling in miniature a ripe cucumber. So 

 intimate was its connection to the abdomen of the crab, 

 that at first it appeared to me to be an abnormal structure 

 connected with the organs of generation ; but, on a careful 

 examination of the points of connection, and upon dissecting 

 the sac itself, I was led to consider it a distinct animal. Hav- 

 ing convinced myself of its individuality, I consulted all the 

 British works devoted to the consideration of parasitical ani- 

 mals, hoping to find it described in some of them, but my 

 labours were without success. Last January, having had oc- 

 casion to consult the Annals of Natural History for Septem- 

 ber 1855 on an altogether different subject, I had the good 

 fortune to meet with the translation of a paper by Professor 

 Steenstrup, in which he discusses the true nature of these pa- 

 rasites. Upon reading this paper, I not only found the para- 

 site I had observed on the Pagurus Bernhardus referred to, 

 but also another described as infesting the Carcinus mamas. 

 At the next low tide I visited the shore of the Firth at Joppa, 

 and my search was rewarded by a plentiful supply of speci- 

 mens of the last-mentioned parasite. The specimens were 

 chiefly found on the Cancer pagurus — the C. mamas supply- 

 ing me with very few. 



The bibliography of the subject is very extended, embracing 

 the various opinions which have been advanced by Cavolini, 

 Rathke, Schmidt, and Steenstrup, as to the systematic posi- 

 tion of these parasites. From the conflicting views which 

 have been advanced regarding the true nature of these enig- 

 matical parasites we are led to appreciate the difficulties of 

 the subject, and warned against rash generalizations. From 



