OF THE CYSTIC ENTOZOA. 85 



II. OF ASTOMA. 



Astoma acephalocystis is an animal very nearly allied to Ace- 

 phalocystis.* It was found attached to the peritoneum of an old 

 subject, generally by means of a broad basis, but very often by a 

 slender pedicle. The sac, composed of three membranes, of 

 more or less delicacy, was very strong, and the membranes were 

 easily separable from one another. They were all more or less 

 composed of fibrous texture, and as in the Acephalocystis the ex- 

 ternal appeared to serve as a means of defence, while the two 

 inner were devoted to nutrition and generation. The young 

 cells, after acting for a time as the organs of nutrition, become 

 free and independent animals after having thrown off young cells 

 internally, which in their turn act as organs of nutrition to their 

 parent, until they are fit to become independent animals them- 

 selves. The particulars relative to the peculiar mode of develope- 

 ment of this animal will be adverted to more at length, when we 

 come to treat of that function in Diskostoma, in the meantime a few 

 remarks on the external character of the animal may be useful. 



It was of a greenish yellow colour when taken from its habitat, 

 and varied in size from a millet seed to that of a middle-sized 

 orange. The smaller specimens were all spherical, and very 

 much corrugated ; the larger were quite smooth and botryoidal 

 the first of which appearances arose apparently from the distention 

 caused by the young ; the second, from the young within it en- 

 creasing irregularly in size. When a section was made of an 

 adult specimen, the interior was found to consist of an immense 

 number of young in various stages of advancement, and all of 

 them apparently having their origin from the enclosing sac, 

 either immediately or mediately. Along with these the inter- 

 stices contained a great quantity of gelatinous matter, which 

 appeared to be the assimilated food, analogous to the pabulum 

 of the seminal cells, already spoken of in another paper. 



* Edinburgh Medical and Surgical Journal. No. clxi., p. 14. 



