480 On the Development and Minute Anatomy of the Infusoria, 



spacC; and the half of the original germ-nucleus, which often 

 remains clearly connected with the other half. " This appear- 

 ance cannot be reconciled with the idea of a defined intestinal 

 canal running circularly through the body of the Vorticella and 

 beset with stalked stomach-vesicles ; for since the posterior half 

 of the body, before the commencement of the diagonal fission, 

 showed just as numerous nutritive masses (stomach-vesicles) as 

 the anterior, it is clear that this half must have contained a seg- 

 ment of the intestinal canal. By the cleft along the line of fission, 

 the intestinal canal, like the germ-nucleus, must have been cut 

 through in two places, and then it would have been impossible 

 for the anterior half of the animal to go on taking nourishment -, 

 but there must have been a time of rest, during which a new uni- 

 ting segment must have been developed between the two widely 

 separated portions of the intestine.^^ 



Prof. Stein proposes the following revision of the Vorticellin^ 

 (Ehr.) j the Stentors to be excluded, as they are ciliated oyer their 

 whole surface. ^^ b^eobcrs sdi 



.y Vorticellinae. ^,> f...;t.*rw, « 



,/,](!. SfalklesSj free swimmers : Trichodina, Urocentrum. 



2. Stalked ; stalk contractile : Vorticella, Carchesium, Zootham- 

 nium. 



3. Imbedded in a common gelatinous investment : Ophrydium. 



4. Inclosed in a cup-shaped cell : Vaginicola, Cothurnia, Mitim- 

 nus, Lagenophrys. 



5. Provided with a non-contractile stalk : Epistylis, Opercularia. 



6. Wholly non-contractile bodies : Spirochona. 



Of these, he says, that he has evidence that Vorticella, Vagi- 

 nicola, Cothurnia, Epistylis, and Opercularia possess distinct Aci- 

 neta-forms. ; ,, 



EXPLANATION OF PLATE XVL D. 



Fig. 1. Full-grown encysted Vorticella microstoma : a, the retracted oral 



circlet of cilia; b, the nucleus; c, the contractile space. 

 Fig. 2. A cyst separated from its stalk. 



Fig. 3. The same more advanced. The nucleus has broken up into spore- 

 like globules. 

 Fig. 4. The same still more developed. The mother-cyst or original body 



of the Vorticella, d, has become sacculated, and many clear spaces 



have appeared in it. 

 Fig. 5. One of the sacculations of the mother-cyst has burst through the 



envelope and has given exit to the gelatinous mass e containing 



the spores. 

 Fig. 6. Acineta-form of Vorticella microstoma, which has arisen from a 



cyst similar to fig. 2 : b, nucleus. 

 Fig. 7- The stalked Acineta-form of V. microstoma, until now described as 



Podophrysjixa : /, the young Vorticella, the result of the trans- 



formatiou of the nucleus of the parent. 

 Ft^r. 8. The young, free Vorticella : a, b, Cy as in fig. 1 ; g, posterior circlet 



of cilia. 



