Spermatogenesis in spiders. 513 



franin and gentian violet. The Ehrlich-Biondi-Heidenhain triple 

 stain was used in a few cases as a differential stain. 



Two methods were employed in making drawings. Following 

 the method of Wilson (IV), photomicrographs of the cells were made 

 and these were enlarged on bromide paper. Then with a pen and 

 waterproof ink, the outlines of the cell structures were drawn in. 

 The photograph was reduced until no color was left and the drawing 

 was completed by hand. This method has given very accurate 

 outlines of the cell boundaries, of the chromosomes, et cetera, but it 

 seems doubtful if the accuracy is commensurate with the time and 

 labor involved. Considerable difficulty was experienced at first in 

 finding a reducer which would leave the bromide paper colorless. 

 Finally, the "Farmer's Reducer" of photography was used with entire 

 satisfaction. Part of the drawings were made by the method just 

 outlined. The rest were made with the aid of a camera lucida and 

 a 1.9 mm Bausch & Lome oil immersion. 



Repeated attempts have been made to secure comprehensive 

 photomicrographs of the cell structures but without success, because 

 of a lack of sufficient depth of focus. 



In cross section the spider testis appears more or less circular 

 in outline, and, as has been pointed out by Wallace, each section 

 usually shows all orders of the germ cells. On the periphery of the 

 testis, we find a general circle of spermatogonial cells and just 

 within we have the cysts containing' the spermatocytes of the first 

 order. Inside of these, we have the cysts containing- the spermato- 

 cyte cells of the second order, with the spermatids lying on the 

 lumen of the testis. This order of arrangement, while typical of 

 most spiders, is subject to much individual variation. Position is 

 never a safe criterion in judging the order of a cell. There is no 

 difficulty however, in the case of the primary and secondary sper- 

 matocytes, in distinguishing the different kinds of cells because of the 

 size relations of the two. The spermatogonial cells and the spermato- 

 cytes of the first order are nearly the same size, but the type of 

 division here is so different, that, after a little experience, one may 

 say with certainty to what order the cell in question belongs. 



The maturation divisions take place with great rapidity in 

 spiders so that it often happens that in the same cyst we have 

 primary and secondary spermatocytes. This fact is of service as it 

 often helps to determine the sequence of the changes going on within 

 the cells. 



