DESCRIPTION OF PLATES 



All figures on plates 1 to 7 were made with the camera lucida, under a magni- 

 fication of 1800 times. The figures photographed are shown on plates 8 to 10. 

 All photographs, with the exception of figures 78 to 81 are magnified 770 times. 

 The magnification of figures 78 to 81 will be given next to their description. All 

 photographs were taken by the author and none of them were retouched in any 

 manner whatsoever. Figures 78 to 110 are of Cambarus virilis, and figures HI to 

 114 are of Cambarus immunis. 



ABBREVIATIONS 



C, centrosome R, radial arms 



I, idiozome V, vescicle 



k, chromatoid masses X, globule 



K, chromatoid bodies Z, cytoplasm 



M, mitochondrial granules Zw, zwischenkorper 



A'', nucleus 



PLATE 1 



All figures from Cambarus virilis 



EXPLANATION OF FIGURES 



1 Resting spermatogonial stage; within the cytoplasm three chromatoid 

 masses, k, are seen. 



2 Late spermatogonial prophase showing the chromatin of the nucleus 

 broken into a great many clumps, preparatory to division. 



3 Metaphase, spermatogonial stage. 



4 Polar view of the metaphase during spermatogonial division showing 200 

 chromosomes. 



5 Anaphase, spermatogonial stage; the centrosome at one pole is double in 

 nature. 



6 and 7 Telophase, spermatogonial stage; in figure 7 the zwischenkorper, 

 Zw, is distinctly seen. 



8 Resting primary spermatocytes. 



9 Leptotene stage. 



10 Synizesis stage. The leptotene threads are observed in parallel pairs 

 migrating to one pole of the nucleus. 



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