A Cytological Study of the Semi-parasitic CopeiDod, Hersilia apodiformis etc. 405 



Textfignre C. 



fluid. The testes proper, as paired tubes, run caudad, tlien make a 

 Sharp turn ventrally and run cephalad. The seriation of the stages in 



the spermatogenesis (Plate IV, Fig. 1) is all 

 that could be desired. In niature individuals 

 the dorsal tube and the bend of the testis is 

 composed of spermatogonia — the most active 

 Zone of niultiplication being just posterior to 

 the "Keimpolster". In the ventral tube, running 

 cephalad, one finds in sequence the various 

 stages in the growth of the spermatocj^tes. The 

 pre-leptotene, leptotene and conjugation stages 

 are followed by a large nuniber of cells in the 

 bouquet stage. The strepsinema conies next, 

 shown by only a few cells in each testis; and 

 then follows the condensation of the threads 

 into compact tetrads, this being more abun- 

 dantly represented. The maturation divisions, 

 which are never numerous, are next in order; 

 and last (most anterior) the zone of metamor- 

 phosis where the round spermatids develop into 

 long-tailed spermatozoa which. when mature, make their way along the 

 ventral walls of the testes into the underlying seminal vesicles {vsl. 

 sem., Figs. A—B). 



Immature female, dorsal view. 



X 52. 



d. g., dorsal groove; l.d., lateral 



depressions for attachment of 



male; o. v., ovary. 



B. Ovaries. 



The ovaries are built on the sanie general plan as the testes (Figs. A, 

 B, C, and Plate IV, Fig. 3) and show a beautiful sequence in the seria- 

 tion of the younger stages. Dorsal and medium in the thorax lies an 

 oval "Keimpolster" {hp., Figs. A—B); and on eitlier side of this "Keim- 

 polster ' the ovaries begin as narrow paired tubes, which first run caudad 

 for a Short distance. This part is composed of oögonia and oöcytes pre- 

 vious to the bouquet stage. The tubes then bend sharply and run cephalad 

 and laterad. At the bend and for a short distance farther, the oöcy- 

 tes are in the bouquet stage (Plate IV, Fig. 3). These are followed by 

 oöcytes of gradually increasing size (Fig. JL); and then (in individuals 

 which have not recently laid) by large eggs, all in practically the same 

 stage and arranged in four niain groups, right and left. The first matura- 

 tion spindle is formed in the uterine eggs before they are laid. The ovi- 

 ducts {oklt, Figs. A—B) pass caudad on either side of the intestine, 

 come into connection with the large spermatotheca, and terminate dor- 



