482 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



out the slightest vestige of suckers. I had made out the 

 existence of teeth, and was anxious to determine whether or 

 not the animal was allied to the cephaloid hydatids. 



The next form of Acephalocystis is one presenting a 

 structure peculiar to itself, and which at once distinguishes it 

 from the others. The external membrane is gelatinous and 

 delicate ; the germinal one is more fibrous, and is so slightly 

 attached to the external one as to float in the contained fluid. 

 When a small portion of this germinal membrane is placed 

 under the microscope, its free or internal surface presents the 

 following appearances : — 1st, A fibrous texture forming the 

 basis of the membrane ; 2d, A series of large irregular ovoid 

 vesicles, arranged in irregular rows. The fibrous texture sur- 

 rounds the vesicles, and thus presents a peculiar appearance 

 of ramification of a very regular form. Each of the vesicles 

 contains one or more dark spots containing nucleoli — these 

 spots are the young hydatids.* 



II. — OF ASTOMA. — (Plate XT.) 



Astoma acephalocystis is an animal very nearly allied to 

 Acephalocystis.f 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 external appeared to serve as a means 

 of defence, while the two inner were devoted to nutrition and 



* This species I have named Acephalocystis Monroii, after Dr. Monro, to 

 whom I am indebted for the opportunity of examining the species, and from 

 whom also I have received much valuable information regarding hydatids 

 generally. A very beautiful figure of A. Monroii is given in Dr. Monro's work 

 on The Morbid Anatomy of the Stomach and Gullet. 



t Edinburgh Medical and Surgical Journal, No. clxi. , p. 1 4. 



