CLASSiriCATION O! THE AKIMAL KINGDOM. 203 



gests caution in assuming that they are all devoid of nuclei, it is 

 probable that the great majority of the Foraminifera resemble 

 Frotogenes and belong to this division, the extent of which will 

 doubtless be greatly enlarged by the discovery of new forms. 



2. The Endoplastica. — The application of the term " nucleus " 

 to the structure commonly so called in this division of the Pro- 

 tozoa, to a certain extent implies a belief in its being homologous 

 with the histological element to which the same name is applied ; 

 and I prefer to revive a term I once proposed for the latter, and 

 to call the body at present in question " endoplast." It may or 

 may not be the horaologue of the histological nucleus ; and with- 

 out expressing any definite opinion on that subject, I wish to 

 leave it open for further consideration. 



It is remarkable that among these Endoplastica there is a series 

 of forms which run parallel with the Monera. Thus Amcebai^Yike 

 a Protamoeha with a nucleus and, commonly, a contractile vesicle. 

 The Infusoria Flagellata are comparable to Protomonas with the 

 same additions, and attaining a considerable degree of complexity 

 in Noctiluca. 



The G-regarinidsB repeat the series of forms oiMyxastrum, though 

 some become divided into several segments, and, as E. Van Bene- 

 den has shown, acquire muscular fibres. 



The Acinetidse and the Eadiolaria apparently have their moneral 

 representative in Actinophrys sol, though the conversion of the 

 pseudopodia into suckers in the Acinetidae distinguishes them re- 

 markably. 



On the other hand, while no monei'al trichopod seems yet to 

 have been discovered, the trichopod type is richly represented, in 

 this division, by the Catallacta of Haeckel, and by the Infusoria 

 Ciliata, of which I think the Catallacta should form only a sub- 

 division. 



It is among the Ciliata that the Endoplastica attain their greatest 

 degree of complexity, by a process of direct differentiation of their 

 protoplasmic substance into tissues and organs, without the inter- 

 vention of cell- formation. 



I have recently examined several genera of Infusoria {Para- 

 mecium, Balantidium, Nyctotherus, Spirostomum) with great care 

 — using very high microscopic powers (1200-2000 diameters), 

 employing osmic acid (which at once kills and preserves un- 

 changed the tissues of the Infusoria) and other reagents, and 

 comparing them with such truly cellular organisms of similar size 



