PLATE 6 



EXPLANATION OF FIGURES 



49 Section through part of gonad shoAving first indications of female de- 

 velopment, i.e., presence of many primordial egg colls surrounded by follicle 

 cells. Gonad consists of almost solid strands. X 681. Length of specimen, 

 10 mm. 



50 Section through wall of gonad in neuter specimen 10 mm. long with 

 thin, smooth shell. 50a and 506 drawn at same place, but at different foci. 



51 Section through an immature female gonad during later oogonial divi- 

 sion and early nuclear changes of oocytes. X 681. 



52 Section through immature female gonad during later nuclear changes 

 and formation of growing oocytes. Follicle nuclei become very much enlarged 

 as oocytes develop, and in adult ovary many more are present than in this 

 figure. 



In the larger of the two resting oocytes in the figure, there is very little 

 matter in the nucleus which takes a chromatic stain. The basichromatin at 

 least is limited to a few granules disposed here and there on the linin threads. 

 Some of these granules lie at the very periphery of the nucleus, and just outside 

 in the cytoplasm there are many granules which have a similar appearance. 

 Whether chromatin is escaping into the cytoplasm, or whether chromidia are 

 appearing in the cytoplasm, must be determined by specific stains for chromidia. 

 X 681. Length of specimen, 17 mm. 



53 to 59 Apyrene spermatosomes which are degenerating during meta- 

 morphosis. All X 1024. 



53 Beginning of degeneration shortly after formation of nuclear vesicles. 

 The cell has several large vacuoles. Two centrioles appeared at extreme edge. 



54 Nuclear vesicles breaking up. Cell outlines irregular. 



55 Degeneration while the axial fibres are growing out. The cytoplasm is 

 full of large vacuoles. 



56 Spermatosome in which all the nuclear matter has disappeared, but no 

 fibres have grown out. 



57 Degeneration during outgrowth of the axial fibres. 



58 Degeneration during outgrowth of the axial fibres. This spermatosome 

 resembles Kuschakewitsch's figure of the nearly adult apyrene spermatozoon 

 of Vermetus. 



59 Degeneration after the apyrene spermatozoon has become nearly adult. 

 The cytoplasm is in small globules and the axial fibres are thus left close together 

 in a strand. 



60 Adult eupyrene spermatozoon. 



61 Adult apyrene spermatozoon. 



64 



