Protozoa. 23 



animals Protoplasta (first tissue). The amount of 

 this differentiation is in some scarcely recognisable, 

 while in others, the sun animalcules or Heliozoa 

 (fig. 10), there are many nuclei, and each of the fine 

 ray-like pseudopodia exhibits distinctly an inner 

 axis of the granule-holding protoplasm and an outer 

 layer of firmer material. These animals multiply 

 by division, and in modes of feeding, &c, they re- 

 semble the Rhizopods, with which they are often 

 united. 



Class 3. GregarinaB. A group of curious parasites, 

 the Grtgaritta, manifest a similar process of differentia- 

 tion taking place in their life-history. 

 These minute creatures are found in 

 the digestive canals of beetles, earth- 

 worms, &c., and in their mature states 

 they appear as elongated bodies with 

 a firm outer wall which never be- 

 comes protruded, and consequently 

 does not allow of the formation of 

 pseudopodia (fig. i, A, B). This 

 outer stratum may itself consist of A . Gregarine f.om the 

 two layers; while internally the 

 protoplasm contains a solid nucleus. 

 At a certain stage in its existence becuia. 



P c. Boat-shaped body 



the adult Greganne becomes almost 



... . , D. Amaebiform body 



globular and quiescent, loses its set free from Pseudo- 

 nucleus, and its internal material 

 becomes aggregated into many boat- shaped bodies, 

 contained within the firm outer layer through which 

 they eventually burst ; each of these boat-like bod-.es 

 (fig. nc) consists of a rigid outer case and an inner 



