4M 31isceUaneous, 



The young individuals observed by the authors did not possess the 

 least trace of a vascular system, or of generative organs. 



The Pilidia, larvce of Nemertina. 



The observations of the authors completely bear out those of 

 Krohn, which show that the Nemertes {Alardus, Busch), which is 

 generally found in Pififlium, is not a parasite upon those animals, 

 but that it is produced by them, by means of a sort of gemmation. 

 Besides the common species {Pilidium gijrans), the authors have in- 

 vestigated a new species, which they call P. auriculatum. They liave 

 arrived at highly interesting results ; they sliow that certain worms 

 of the Order Neinertince present a mode of development which may 

 be brought into complete parallelism wath the remarkable genetic 

 history of most Echinoderms. The development of the Nemertes in 

 its Pilidium is precisely the same with that of an Echinus or an 

 Ophiura in its Pluteus. But, whilst in the Echinoderms it is only 

 the stomach of the larva that passes into the perfect animal, not only 

 the stomach, but also the oesophagus and the mouth of the Pilidium 

 are preserved in the Nemertes. 



Tomopteris. 



The authors demonstrate that Burmeister was wrong in classing 

 Tomopteris among the Mollusca. They are true Annelides, as 

 Grube first maintained. It would even appear that their most natural 

 position is beside Chcetopterus. 



Sagitta germanica. 



Although the anatomy and a considerable portion of the develop- 

 ment of the Sagittce have been sufficiently made known by the 

 works of Wilms, Krohn, Gegenbaur and others, the recent state- 

 ments of Meissner (1856) upon the evolution of these little animals 

 give a particular interest to the researches of MM. Leuckart and 

 Pagenstecher. In fact, although most observers are now agreed in 

 classing the Sagitt(E among Vermes, Meissner succeeded in unset- 

 tling the faith of some people, by describing in the young Sagittce 

 of the sea of Heligoland a chorda dorsalis and a spinal cord, — in a 

 word, organs which appear to give this animal a place amongst the 

 Vertebrata. The investigations of the authors, made upon the same 

 species that was studied by Wilms and Meissner, show that the older 

 authors were not deceived in placing the Sagittce amongst the true 

 W^orms ; and these two observers cannot at all account for the 

 evidently erroneous statements of Meissner. 



Echinobothrium typus. 



This Cestoid worm, which has already been studied by Van Be- 

 neden and others, lives as a parasite in various species of Hays. The 

 authors have been able to trace its development, which precisely 

 resembles that of other worms of the same Order. In the least ad- 

 vanced stage observed by the authors, the animal presents the form 

 of a vesicle (embryonal vesicle), of which one of the poles exhibits a 



