482 Mr. H. D. S. Goodsir on the Develojmient of Ac&phalocysts. 



parent vesicle ; by the rupture of this membrane they escape into 

 the parent cavity and become independent creatures. The external 

 or tubular membrane, when placed under a powerful glass, was found 

 to be studded with numerous small shining vesicles ; these he con- 

 siders to be the gemmules of this hydatid, which, like other Acepha- 

 locystic Entozoa, is gemmiparous. In addition to the two modes of 

 propagation now stated, for the purpose of increasing the size and ex- 

 tent of its own individual group, this Entozoon has another whereby 

 it can extend the species to uniufested portions of an infested animal ; 

 the cells which have been described as floating free within the body 

 of the parent hydatid reach the healthy tissues which lie at some 

 distance from the parasitic mass by some means which the author has 

 been hitherto unable to detect. In general they are no deeper than the 

 subserous tissue, but as they increase in size they always tend to- 

 wards the surface of the infested cavity, and at length burst from their 

 confinement, adhering at the same time to the bottom of their former 

 locality by pedicles containing cellules. In another form of Cystic 

 Entozoon, the Canurus cerebruUs, which is met with in the brain of 

 sheep and other Ruminants, the external membrane presented an ap- 

 pearance similar to that of the tubular membrane of the new Ace- 

 phalocyst, although not so strongly marked. Numerous heads, armed 

 superiorly with a double circle of hooks, are implanted by means of 

 pedicles upon the external surface of the cyst. Now it is within 

 these pedicles that layers of rejjiroductive gemmules are found which 

 exhibit in their earliest stage pai'ts very analogous to those in the 

 ovules of the higher animals, and are developed at first in one plane 

 only from the germinal spot, but subsequently in a direction per- 

 pendicular to the original plane ; the former of these is termed the 

 discoidal, the latter the vertical period of development. These and 

 other more minute details, which we must pass over, since without 

 the plates they would not be sufficiently intelligible to the general 

 reader, prove that the development of the Ccenuri is more compli- 

 cated than in the Acephalocysts. The author concludes his paper 

 by tracing some very curious analogies between the forms of Cystic 

 Entozoa and those of other classes of the animal kingdom in the fol- 

 lowing words ; — 



" Beginning with what I conceive to be the lowest form of Ento- 

 zoon at present known, the simple hydatid, I find in it the analogue, 

 in its own class, of the typical forms of the Infusoria, as the Volvo- 

 cince. 



" Proceeding to the new form of hydatid described in this paper, 

 I consider it as the analogue of the Polypifera, and of such forms as 

 have Alcyonidium for their type. In both we find the same general 

 basal mass, and the same mode of nutrition, in the hydatid, by means 

 of disc-bearing stomata, each disc analogous to a polype, and in the 

 Alcyonidium by tentaculated heads with stomach cavities. Both 

 forms also are compound, the general group deriving nourishment 

 from the individuals, and the individuals deriving support from the 

 group ; so that in both cases, the general mass and individual stomata 

 or polypes mutually tend to s\ipport one another. Both have two 



