260 T. W. Engelmann on the Infusoria, 



into one large body, which by and by breaks up into eight seg- 

 ments, from each of which four germs proceed. The segments 

 so subdividing generally present about their centre a fissure-like 

 fold, recalling what happens in the nucleus of Aspidisca, Eu^ 

 plates, and Oxytrichina under like circumstances. On the water 

 around the Gastrostyla drying up, the animal readily encysts 

 itself, the cysts resembling those of Stylonychia MytiluSj but 

 rather more indented on their surface. 



In company with Gastrostyla and Cyclidium glaucoma, some 

 small circular Acinetce were sometimes met with, resembling the 

 embryos of Stylonychia Mytilus, and not improbably embryos of 

 the Gastrostyle itself. This, however, is uncertain, as specimens 

 of this animalcule were discovered with embryonic corpuscles. 

 Size 0-15 to 0-32 mill. 



AsTyLozooN. PL III. fig. 20. 



Body contractile, unstalked, campanulate, with an acutely 

 pointed posterior extremity having a curve backwards. Surface 

 smooth. Rotary organ extrusile, furnished with a spiral ciliary 

 wreath. Peristome swollen, thickened. Posterior extremity 

 terminated by one or two long locomotive setae. Nucleus short, 

 reniform, 



A. fallax, PI. III. fig. 20. 



The only species known. At first sight, it looks like a de- 

 tached Vorticella microstoma, but differs from it by its curved 

 posterior pointed extremity, its rotary organ becoming wider 

 behind obliquely, its small reniform nucleus, and its terminal 

 locomotive setse, whereby it can execute movements not efi'ected 

 by any detached VorticellcB. It is frequently encysted. Size 

 0-1 mill. Size of cysts 0038 to O'Oo milL 



EXPLANATION OF PLATE IIL 



Tig. 1. Euplotes Charon, in process of conjugation. 



Fig. 2. The same animalcule at a later stage of conjugation : the new 



system of cilia is further developed, and the two beings are in 



course of separation. 

 Fig. 3. The globular vesicle developed internally has attained about its 



maximum growth. 

 Fig. 4. Stylonychia pustulata, in conjugation. The anterior extremities of 



the two animals connected by an intermediate band. 

 Fig. 5. The same, in conjugation according to a second variety of that 



process. The tv/o beings, united most of their length, have 



begun the development of a new series of cilia. 

 Fig. 6. The same animalcules two hours later. 



Fig. 7. One of the animalcules after the termination of conjugation and 

 ^ separation, twenty minutes after the stage shown in fig. 6. 



