86 OF THE ANATOMY AND DEVELOPEMENT 



III. OF DISKOSTOMA.* 



Diskostoma aceplialocystis is anotlier animal belonging to the 

 Cystic Entozoa, and very similar in many respects to the pre- 

 ceding genera ; it is, however, more complicated in its structure 

 than either. 



Diskostoma was met with in great numbers in the peritoneal 

 cavity of a middle-aged man. About six or eight gallons were 

 taken out of the abdomen after death, all of which had been ap- 

 parently generated in the course of a few months.t Like Astoma 

 they varied very much in size, but with very few exceptions 

 were all regularly globular, and of a bright straw colour, hang- 

 ing, when undisturbed, from the surface of the abdominal cavity, 

 like the ova in the active ovarium of the common fowl. The 

 sac consisted of two demonstrable membranes, the most external 

 of which was rather complicated. 



The basis of the membrane itself was nbro-gelatinous, and 

 having a number of discs scattered at irregular intervals over its 

 surface ; these discs were connected with one another by means 

 of numerous tubuli, which also ramified freely through the mem- 

 brane. These were probably the organs of nutrition. The next 

 membrane was much more delicate, and was that from which the 

 gemmules arose. In some instances there was the appearance of 

 a third membrane, but it was most difficult of detection. The 

 greater mass of the body was composed of the gelatinous matter 

 already alluded to as occurring in Astoma. 



The function of generation in all these lower Acephalocysts is 

 very interesting. In all of them the young cells, or gemmules, 

 arise from the middle membrane of the sac. In Aceplialocystis 

 and Astoma the young cells act at first as organs of nutrition, 

 and after a time become themselves independent animals. This 

 is probably the case in Diskostoma also, but it could not be de- 

 termined with certainty. The mode of devolopement of the 

 young in Astoma and Diskostoma is somewhat different from that 



* Transactions of the Royal Society, Edinburgh, Vol. xv. p. 564. 



t See Edinburgh Medical and Surgical Journal for October 1844, page 1. 



