246 



H. M. WOODCOCK. 



Resting, intracellular phases (the " Leucocj'tozoon " of Danilewsky and 

 the "Hsem amoeba "-stage of Laveran) of these sexual forms are shown 

 in fig. 33 c (male) and E (female). In both gametocjtes the greater part 

 of the body (endoplasm) becomes retracted into an ovoid mass; the ecto- 

 plasm with its myonemes, in conjunction with the cytoplasmic envelope of 

 the host-cell, alone retains the original spindle-shaped outline of the para- 

 site.* No trace of the flagellar apparatus is left, and the kinetonucleus 

 takes up an internal position, close to the trophonucleus (fig. 33 c). 



Fig. 34. 



Fig. 35. 



Fig. 34. — Formation of the eight microgametes from the micro- 

 gametocyte in T. ziemanni. The unused cytoplasm breaks up 

 into three or four residual masses. 



Fig. 35. — Fertilisation of a megagamete by a microgamete. 

 The tropliic and kinetic female pronuclei are seen on tlie left. 

 Near the centre lie the two reduction-nuclei. 



In both figures the remains of the host-cell, together with the 

 cast-off ectoplasmic envelope of the parasite, are seen on the 

 right, (After Schaudinn.) 



The gametocytes in this stage are, of course, to be met with in the peri- 

 pheral circulation, and when introduced (with the blood) into a gnat during 

 the act of biting the}' at once proceed to gamete-formation. A fully grown 

 microgametocyte may undergo the requisite nuclear changes and multipli- 

 cation while still in the blood of the owl, and it is this process actually 

 which is beginning in the individual seen in fi<r. 33 E.' Eight double nuclei 



' Laveran (37), it may be noted, figures also rounded or spherical forms 

 of the gametocytes and their host-cells, but Schaudinn does not mention 

 the occurrence of such. 



- In some cases apparently the microgametes may even be formed and 

 liberated from the parent-cell while in the blood. Laveran (1. c.) figures 



