170 JULIAN S. HUXLEY. 



'I 



(2) The presence of a special cup-like structure at the 

 posterior end, which co-operates with the epimeritic organ 

 at the anterior end to effect a close union of two individuals 

 during association. Association is thus by dissimilar ends, 

 and lasts for some time. 



(3) The eventual complete cytoplasmic fusion of the 

 associated couples, and the existence of a second trophic 

 phase, when the animals grow very fast, but are morpho- 

 logically quite degenerate. 



(4) The position of the nucleolus in this phase, on one 

 side of the nucleus, partly in contact with the cytoplasm. 



(5) The habitat, in the gut and liver of Syncaridan 

 Crustacea. 



Considering these characters in relation with other members 

 of the class, we find that no known Gregarines inhabit the 

 liver of any Crustacean ; none have the nucleolus in the same 

 position; none go through two trophic phases; none have 

 any special structure for association at the posterior end ; 

 and none have a protrusible organ of the same sort at the 

 front end. It is thus at least obvions that Ganymedes is the 

 representative of a very divergent line. The suggestion I 

 would make is that, while nearer to the Monocystid type, 

 Ganymedes is partly intermediate between the two great 

 groups of Eugregarines, as represented diagi-ammatically in 

 the following tree : 



Polycystidea. Ganymedes. Monocystidea. 



Ancestral Eugregarines. 



