THE H.^MOFLAGELLATES. 



193 



resting condition. There are now two almost equal-sized 

 nuclei lying contiguous to, and on opposite sides of, tlie larger, 

 central, pi-obably tro])liic one, namely, the old kinetonucleus 

 and the newly-formed body. Each of them next divides 

 twice (the old kinetonucleus may have commenced before, as 

 in [b]), cutting off successively two reduction-nuclei (c and 

 D, r.n.), which are gradually absorbed by the cytoplasm. The 

 reduced kinetonuclear elements penetrate into the resting 

 trophonucleus from opposite sides (d, r.k.e.), and fuse to form 



f --C./7 



D. ^E. 



!-yF. 



Fig. 11. — Parthenogenesis of a gregaviniform female, r.n. = 



residual nuclei ; r.fc.e. := reduced kinetonuclear elements; c.n.= 



compound nucleus, equivalent to that of an ookinete. (After 

 Schaudinn.) 



the central kinetonucleus (e and p), exactly as do the reduced 

 kinetonuclei of the male and female gametes, after fertilisa- 

 tion. After this double process of parthenogenesis and 

 '^ self-fertilisation," the gregariniform parasite can develop 

 along any of the three lines above indicated. The actual 

 course taken is, doubtless, largely determined by the existing 

 condition of the cytoplasm as regards nutritive material, and 

 by its size relative to that of the nucleus. 



The three types of parasite above described include all the 

 varieties of form met with in the gnat. From the standpoint 

 of reproduction the indifferent Trypanosomes are by far the 

 most important^ the capacity for longitudinal fission being, 



