SPERMATOGENESIS OF THE DRAGON-FLY. 27 1 



the testes of certain other insects, but consist of globular cysts 

 arranged one or two layers deep around a central duct which 

 runs through the organ in more or less of a zig-zag course. 

 Each testis is of nearly uniform size along its entire length, 

 tapering at the posterior end where the vas deferens emerges. 

 The epithelium covering it is thin and hidden by a layer of 

 fatty tissue which contains tracheae. The central duct has a 

 thick epithelial wall and each cyst, surrounded by a thin layer 

 of epithelium, apparently opens into the central lumen by a 

 separate duct. All the developing stages of the spermatozoa 

 may in favorable preparations be found in one cross-section. 

 The cysts seem to have no definite arrangement in the tubule 

 according to the age of the products. One containing primary 

 spermatocytes may lie between two containing mature sperma- 

 tozoa. As a rule all the cells in each cyst are at the same stage 

 of development, although two or three primary spermatocyte 

 divisions may occur occasionally in cysts containing older 

 products. Where the cell is passing rapidly through the later 

 prophase stages which precede the first maturation division, 

 cysts containing two closely successive stages occur. In the 

 older cysts which contain spermatozoa, there is a shrinkage in 

 size and the cysts become separated by large spaces. Fig. 2, 

 a cross-section of a whole testis, shows the central duct with its 

 thick epithelial wall; the cysts containing products at different 

 stages of development; and the fatty layer containing the 

 tracheae and covering the outer epithelium of the testes. In 

 some testes degeneration had taken place in a few cysts con- 

 taining spermatogonia. Fig. 3, a cyst in which degeneration 

 had taken place, shows how the chromatin condenses into a 

 solid mass in the nucleus of each spermatogonium. 



In the female larva, the ovaries lie in the anterior end of the 

 abdomen, dorsal to the digestive tract and are close together 

 anteriorly, while posteriorly they separate forming an inverted V. 



III. METHOD OF FIXING AND STAINING. 



Injection of the living larva with the killing fluid was found 

 to be the best method of killing and fixing the gonads. A hypo- 



