— 52 — 



choraonads, which ingest food throng-h the cytostome, to the Tri- 

 chonyraphidae, which feed to a certain degree like amoebae. 



One of the obstacles, which make it difficult to derive the 

 Trichonymphidae from the more simply built ]\Iastigophora, 

 is the great difference in size between the two groups. The 

 series of forms just described, found in the intestine of ter- 

 mites — TricJiomonns termitis, Tr. inacrostoma and Giganto- 

 wo72as— remove this obstacle. We sec now, that the Tricho- 

 monads living in the termites may attain enormous sizes, 

 without hardly at all undergoing any morhological changes, 

 owing to some especially favourable life conditions with 

 which they meet in the intestine of the insects named. 



At the conclusion, a few words may be said about the 

 genetic relations between the forms just described. The pre- 

 sence of two species in the intestine of Hodotermes, which 

 are so alike in morphology, and so unlike in size, as Triclio- 

 monas macrostoma and Qigantomouas herculea. maj^ in my 

 opinion, be explained in the manner, that Gigantomonas has pas- 

 sed a much longer period of parasitic life in termites, and 

 is therefore changed much more than Trichomonas. 



IV. Myxomonas polymorpha n. gen. n. sp. 



The amoeboid state, iu which GigantomoJias is found but 

 rarely, becomes constant in this genus. Myxomonas presents 

 a Trichomonad which has assumed the amoeboid form, and 

 lost the cytostome and the anterior, free flagella. Myxomonas 

 is found together with the preceding genus in the intestine 

 of Hodotermes mossambicus Hag. 



The species described is found in the intestine of the same 

 termite in several forms, which differ one from another to a 

 greater or smaller degree, and which present different stages 

 in the cycle of development of the animal. 



We shall begin the description from a stage which resem- 

 bles Trichomonas more closely, and whicli we shall name type A. 



Type A. The body-shape is changeable, amoeboid (tab. II, 

 fig. 17 tl- 18). The sizes of Myxomonas vary considerably, as 

 is seen from the following ratios of length to the maximum 

 width expressed in microns: 28:25, 50 — 40, 55:25, 65:40, 

 70 : 25, 80 : 25. 



The body of Myxomonas is usually clearly differentiated 

 into a thick layer of ectoplasm, and an interior endoplasmatic 



