302 Miscellaneous. 



of the embryo are produced ; the cincture becomes the ciliary fringe 

 of the vestibule, and the uniting membrane the body of the Gypho- 

 nautes. The testis asimple chitinization of the twohalvesof the uniting 

 membrane. The disk, situated between these two halves, is, after 

 the formation of the test, included between the two valves, and 

 thenceforward begins to undergo a complete retrogradation. 



These embryogenical results are confirmed by the comparison of 

 the different types. Between the two extreme forms Alcyonidiwm 

 and Cyphonautes compresstis, two new types of transition (Eucratea 

 and the Cyphonautes of Saint-Vaast) establish an intimate connexion, 

 and constitute an uninterrupted chain, which enables us to trace with 

 certainty the homology of the various organs. 



The larvae of the Vesicularise appear, when hatched, in the form 

 of a regular ovoid, slightly flattened at each pole, and having a 

 general covering of long vibratile cilia. At each pole there is a less 

 coloured spot, indicating the presence of a special organ ; the spot 

 at the upper pole is slightly prominent, and that at the inferior pole 

 completely flat ; the portion of the ovoid situated between the two 

 poles is covered with long, characteristic ribs, and bears, in a longi- 

 tudinal direction, an aperture resembling the pharyngeal fissure of 

 Alcyonidium, and, like it, surmounted by a vibratile tuft. Lastly, 

 to each of the above-mentioned spots there corresponds a system of 

 organs which the opacity of the embryo prevented my distinguishing 

 with the desirable precision. 



The phenomena which produce this strange structure result, as in 

 all other cases, from modifications of the bell-shaped stage. They 

 consist simply in an exaggerated development of the crown, the 

 dorsal and ventral parts behaving exactly as in the ordinary larvae ; 

 but each of the cells of the crown undergoes a considerable growth 

 in a longitudinal direction, and becomes converted into a rib occu- 

 pying the whole length of the embryo. At the close of the develop- 

 ment the whole of these ribs forms a sort of sheath, at each extremity 

 of which projects the rest of the dorsal and ventral surfaces in the 

 form of dark-coloured spots. — Gomptes Rendus, September 6, 1875, 

 p. 443. 



On the Migrations and Metamorphoses of the Marine Endoparasitic 

 Trematodes. By M. A. Villot. 



The marine endoparasitic Trematodes have been much less studied 

 than their terrestrial and freshwater congeners, and we still know 

 little of their development. Hitherto isolated facts have been col- 

 lected merely by chance, and very little anxiety has been shown to 

 find a method which might serve to combine these with each other. 

 Experiment, to which most investigators have had recourse, in such 

 cases could not serve this purpose ; for, even in case of success, it 

 always leaves a great uncertainty as to the normal host of the para- 



