ECONOMY OF THE ACEPHALOCYSTS OF AUTHORS. 5(53 



a considerable size, but decreased very much as it gave off smaller branches in 

 its outward course. Sometimes a tube of considerable magnitude, or rather a 

 fasciculus of tubes, was seen connecting two neighbouring disks. 



Immediately underneath that already described, was another membrane of 

 a much more delicate texture. (PL XV., fig. 5, G.) It was connected with the 

 former by means of condensed cellular texture, and sent off numerous very fine 

 septa, which traversed and intersected the body of the Hydatid, for the purpose, 

 apparently, of rendering it support. The body of the animal itself was composed 

 of a homogeneous gelatinous mass, of the colour and consistence of calf s-foot jelly. 

 The open stomata and tubes, which were seen in the external membrane, appeared 

 to be the organs of nutrition. They could not, however, be traced into the gela- 

 tinous mass, so that, probably, they only existed in that one membrane. 



The mode of generation and of development in these animals is very simple. 

 When the internal surface of the vesicle of the common Hydatid is examined, it 

 will be found studded all over with numerous smaller vesicles of different sizes. 

 (Plates XIV. and XV., figs. 6 and 4.) These, as already stated, are young Hydatids. 

 A simple cell makes its appearance under the internal lining membrane of the 

 parent vesicle, which gradually increases in size, without any cellular develop- 

 ment whatever, but by dilatation alone from the increase of the quantity of 

 matter within it. (PI. XV., fig. 6.) In this way it increases to such a size as to 

 burst through the internal membrane, escape into the cavity of the parent vesicle, 

 and thus become an independent creature. This is the reason why we find the 

 internal surface of the vesicle so frequently broken up. The finest example of the 

 kind which I have seen, is one in the possession of Dr MONRO, and which he has 

 been so kind as allow me to examine. A very fine drawing of this may be seen 

 in his work already referred to, on the Morbid Anatomy of the Gullet, Stomach, 

 and Intestines, at PL IV., and fig. 18. 



When a small portion of the external or tubular membrane of the new form 

 of Hydatid was placed under a powerful glass, its internal surface was found to 

 be studded with a number of small shining bodies or vesicles. In general, these 

 vesicles were compound, containing from one to four young cells in their interior 

 (PI. XIV., fig. 7, FFF) ; which cells, however, were occasionally seen free and 

 detached from the parent one. (PL XV., fig. 3, C.) I considered them to be the 

 gemmules of this Hydatid, which, like the other Acephalocystic Entozoa, is gem- 

 miparous. 



The tubular membrane, as it spreads over the healthy peritoneum, and ap- 

 parently after it has reached a certain stage of growth, developes the cells, just 

 described, from its attached surface, and invariably from spots in the neighbour- 

 hood of the large tubes. (PL XIV., fig. 9, AA.) These gemmules enlarge without 

 any apparent cellular development ; but, like the simple Acephalocyst, by dilata- 

 tion from the addition of new matter within the cell. It varies, however, from. 



