864 THE ANIMAL KINGDOM. 



disappear leaving one in the centre. The spore has no membrane and 

 at either end of it a clear ' polar body' becomes visible. This body con- 

 tains a long internal and spirally coiled thread, which is shot ' out on 

 the application of alkalies, &c. It is therefore a trichocyst, and it is sup- 

 posed that the discharged thread serves to anchor the spore to any soft 

 body into which it may happen to penetrate. The spores of other Myxo- 

 sporidia may be flattened and lens-like with one pole somewhat pointed, 

 more rarely ovate, or fusiform, and pointed at each end. The spore-case 

 is generally bivalved and drawn out into a simple or forked process. The 

 pointed pole is always open, and trichocysts to the number of one, two, 

 three, rarely four or eight, are lodged at the aperture. The escape of an 

 amoebula from the spore-case has been observed. 



There are two Sporozoans of doubtful position, Lithocystis Schneider^ and 

 Amoebidium parasiticum. As to the former, it is found in the coelome of the 

 Spatangid Echinoid, Echinocardium cordatum, on the inner aspect of the test and 

 the outer of the intestine, in the shape of large irregular black masses, perhaps plas- 

 modial in nature. They may attain a size of about f inch long, and \ broad. 

 Adherent to these black masses are a variable number of hyaline spheres -^/j inch 

 in size. Each sphere has a structureless membrane, one, rarely more, masses of 

 crystals which are dispersed in later stages, and a number of spores. The latter are 

 at first disposed round a yellowish spot or mass to which they adhere each by two 

 filaments. During the course of development they become rearranged if the cyst is 

 large enough and adhere by their other extremities, the filaments then looking like 

 rigid flagella. The spore contains a granular protoplasm which is resolved into 3-6 

 falciform bodies, and a residual mass which becomes reduced to 2-3 granules or 

 disappears completely. Giard, who discovered this organism, believes that the falci- 

 form bodies give origin to some of the amoebae, so common in the coelomic 

 fluid. See C. R. 82, 1876, or A. N. H. (4), xviii. 1876, p. 192. 



Amoebidium parasiticum was discovered by Cienkowski. It is a tubular 

 organism, about -5 mm. long and occurs attached by one end to the feet and 

 branchiae of larval Phryganids and Libellulids, and certain freshwater Crustacea, 

 Gammarus, Asellus, &c. The tube has a delicate wall, finely granular protoplasm, 

 often vacuolate, and containing a series of nuclei placed at regular intervals along 

 the axis. The protoplasm segments, a portion to each nucleus, forming small fusi- 

 form bodies which escape and either grow into new Amoebidia, or their nuclei divide 

 once or twice and their protoplasm segments, giving rise to amoebulae. The parent 

 organism may produce similar amoebulae. The latter move about by means of 

 lobose pseudopodia. They either form thick-walled resting cysts, the contents of 

 which eventually break up into a number of fusiform bodies, either within the cyst or 

 after escaping from it inclosed in a delicate membrane, or they form an oval thin- 

 walled cyst the contents of which break up at once in the same manner. By Cien- 

 kowski, Amoebidium was considered to be a fungal ; Balbiani groups it with the 

 Sarcosporidia. See Cienkowski, Botan. Zeitung, xix. 1861 ; Balbiani, op. cit. infra, 

 p. 116; Biitschli, op. cit. infra, p. 611. 



The Gregarinida are classified by Biitschli, op. cit. infra^ as follows : 



