STRUCTURE AND LIFE-HISTORY OF GRITHIDIA MELOPHAGIA. 205 



penetration the blunt end of the flagellate enters the egg 

 first. Occasionally the flagella are cast off as the Crithidia 

 pass into the egg and remain on the outside. 



In the case of older ova, the parasices seem to penetrate 

 the egg- at a definite spot (PL 13, fig. 58), which probably 

 becomes the mouth of the embryo. Parasites invading older 

 embryos enter by the embryonic mouth. Like Swingle I did 

 not find parasites in the milk-glands or milk of Melo- 

 p h a g u s . 



In investigations of the stages of C. melophagia in 

 the egg and puparia I found that smear preparations 

 were preferable to sections. Gi'eater rapidity of manipula- 

 tion and thinner preparations could be obtained by this 

 means. 



The method adopted was to prick the egg or open tlie 

 young puparium and express the contents on to a slide. The 

 contents were at once fixed and then were allowed to flow 

 over the slide, so that no artificial spreading was required, 

 and therefore no mechanical distortion or tearing of the , 

 parasites could occur. The preparations so made contained 

 much fatty matter. The slides were treated with ether to 

 remove the fat, and then after washing with absolute alcohol 

 were stained and mounted in the usual manner. 



Once within the egg the parasite gradually loses its flagel- 

 lum (PI. 13, figs. 61-63). This may be cast off entire, for 

 flagella are found floating freely in the vitellus of eggs that 

 had been treated with the utmost care in the manner pre- 

 viously detailed. In many cases the flagellum appears to 

 be gradually absorbed (Pi. 13, figs. 64, 6d). Longitudinal 

 division of the flagellates in the egg may occur, though 

 rarely. 



The protoplasm of the Crithidia then concentrates round 

 the nucleus and blepharoplast (PI. 13, figs. 64-69) and the para- 

 site gradually becomes more or less rounded (PI. 13, figs. 70- 

 73). Multiple division of both nucleus and blepharoplast 

 then occurs (PI. 13, figs. 74-77), and the daughter-blepharo- 

 plasts appear to pass outwards towards the periphery (PI. 13, 



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