THE CYSTIC ENTOZOA. 491 



internal surface of the cyst, apparently by means of the spines. 

 These bodies, although the intermediate stages between them 

 and the young gemmules could not be seen, I considered to be 

 young Cysticerci in an advanced stage of growth, and I was 

 led to do so because they were often observed on the free 

 surface of the omentum, attracting and puckering it together 

 in folds, evidently the commencement of the process for the 

 formation of a cyst, and in many instances they had completely 

 enveloped themselves. It has not yet been decidedly made 

 out in what manner the gemmules escape from the body of 

 the Cysticercus, but from the observations I have made, it 

 appears that they must first escape from the pedicle where 

 they are formed into the sac, and then from the sac to the 

 cyst. I am led to this supposition in consequence of having 

 observed on several occasions the sac of the animal ruptured, 

 and great numbers of the globular spined bodies attached to 

 the inner surface of the cyst. How they escape from the cyst 

 I have not been able to determine. 



Those Cysticerci having the cyst composed of a double 

 membrane, do not differ in any other particular from those of 

 the preceding division of the genus. The best example of this 

 peculiarity of structure exists in a species found in the liver 

 of the rat, and which I have denominated Cysticercus rattus. 

 The specific characters are given in the synopsis at the end of 

 the paper. 



In all the details, then, we find a great similarity between 

 Csenurus and Cysticercus, with this exception, that the latter 

 is simple, whereas the former, like all the other Acephalocysts, 

 is a compound animal. Why the pedicles of Csenurus should 

 all become attached to the same sac, is a fact, the cause of 

 which it will be impossible to determine with any degree of 

 certainty ; probably, however, it arises from the difference of 

 strength in the sacs of the two animals ; the greater strength 

 of that of Caenurus preventing the escape of the young gem- 



