162 M. Steenstrup on the genera Pachybdella and Peltogaster. 



different forms from the one in which he has figured them. 

 From the similarity to the Cancer paludosus we might almost be 

 induced to suppose, that his figure represents the animal con- 

 tracted into the bowed form in which it lies in the egg, and which 

 it may probably have retained for some moments after exclu- 

 sion, — and the resemblance to the larva of a Cirripede or of 

 some other Entomostracan, might have been produced in this 

 manner. 



All this however lies, as I have already said, beyond the ob- 

 ject which I had proposed to myself in the present communica- 

 tion, and only furnishes indications which I recommend espe- 

 cially to the notice of those naturalists, who for the study of the 

 lower animals have lately so often visited the coast of the Medi- 

 terranean, where these remarkable parasites must, according to 

 the preceding observations, be not uncommon*. 



Postscript. 



Some time since I was informed, by a letter from Dr. Crephn 

 of Greifswald, that Professor 0. Schmidt had given a figure and 

 short description of the larva of a Pachybdella in a periodical 

 called ' Das Weltall ' for 1854 (No. 3. p. 19), but I have only just 

 (December 1854) been able to obtain this journal. From the 

 figure given by Schmidt, which agrees closely with Cavolini's 

 fig. 16 c. referred to by me, it certainly appears that the young 

 animal is extremely like the larva of an Entomostracan ; and this 

 renders still more remarkable the relation above referred to be- 

 tween the LiriopcB of the Peltogastrij which resemble the larvae of 

 Bopyrus, and the Liriope-YikQ young of Cavolini's extraordinary 

 parasite (figs. 17 & 18 r r). Moreover Schmidt^s observations 

 prove that Pachybdella is not only common but even abundant 

 at Wangerooge, and it also appears that Schmidt has collected 

 single specimens of Pachybdella = Peltogaster on the Dalmatian 

 coast. 



t The Peltogastri which I have been able to examine, for three of which 

 I am indebted to the Zootomical Museum of this University, and for a 

 fourth to Professor J. Miiller of Berhn, have unfortunately furnished me 

 with no explanation of the structure of the embryos, as none of them pre- 

 sented eggs with developed larvae. This was also the case with the speci- 

 mens of Pachybdella. 



