EXTOZOA. 45 



chloric acid ; and also of another peculiar substance analogous to 

 mucus.* The fluid of the acephalocysts contains, according to 

 Lobstein, a small quantity of albumen with some salts, including 

 muriate of soda, and a large proportion of gelatin. 



The tunic of the acephalocyst is usually studded with more or less 

 numerous and minute globules of a clear substance (c), analogous to the 

 " hyaline," whose remarkable properties in reproductive cells, Dr.Barry 

 has recently described, and from which the young acephalocysts are de- 

 veloped. No contractile property, save that of ordinary elasticity, has 

 been observed in the coats of the acephalocyst ; no other organisation 

 than that which I have just described ; no other function than that of 

 assimilation of the surrounding fluid by the general surface, and the de- 

 velopment of new cells from the nuclei of hyaline. We see with how 

 little reason such a body can be compared with the Volvox gl abator y as 

 has been done by Professors Nitzsch and Leiickart.f The discovery of 

 the composite character of that low organised Infusory and the elucida- 

 tion of the anatomy of each constituent monad prove the acephalocyst 

 to stand on a still lower step in the series of organic structures. A 

 better comparison is that which approximates the acephalocyst to the 

 Protococci of the vegetable kingdom ; these lowest forms of crypto- 

 gamic plants consisting of a simple transparent cyst, and developing 

 embryo cysts from their external surface. The knowledge that we 

 now possess of the primitive embryonic forms of all animals and of 

 all animal tissues, places us in the position to take a true view of the 

 nature of the acephalocyst. It seems to me to be most truly de- 

 signated as a " gigantic organic cell," not as a species of animal, even 

 of the simplest kind. 



Yet these productions have not escaped the ingenuity and dis- 

 criminative powers of the classifier. Of the numerous species, 

 nominal or real, which are to be found in the works of naturalists 

 and pathologists, I shall notice only two: — 1st, the Acejyhalocystis 

 Endogena of Kuhn, likewise called Socialis, vel prolifera^ by Cru- 

 veilhier : the " Pill-box Hydatid " of Hunter. It is the kind most 

 commonly developed in the human subject, and in which the 

 fissiparous process takes place usually from the internal surface of 

 the parent cyst, the progeny being sometimes successively included : 

 and, 2dly, the Acephalocystis Exogena of Kuhn, Eremita, vel Sterilis, 

 of Cruveilhier, which developes its progeny generally from the external 

 surface, and is found in the ox and other domestic animals. 



And now I can well imagine that some may be tempted to ask, 



* Collard, Diet, de Med. et de Chir. prat. Art. " Acephalocystes." 

 t Tschudi, Die Blasenwurmer, 4to, 1837, p. 29. 



