278 NATHAN FASTEN. 



matogenesis of Carcinus menas, while Binford ('13) hastily 

 described the spermatogenesis of the Atlantic coast edible crab, 

 Menippe mercenaria. None of these investigators, however, 

 have given details regarding the interesting processes of synapsis, 

 reduction, chromosome numbers and the like. 



During the past few years the writer has been gathering testicu- 

 lar material of numerous crabs which occur along Puget Sound, 

 for the purpose of studying their spermatogenesis, and in the 

 following pages the spermatogenesis of one of these forms, namely, 

 Cancer magister, is described. 



2. MATERIAL AND METHODS. 



As already mentioned, the material from which these studies 

 were made consisted of the testis of the common edible crab of 

 the Pacific coast, Cancer magister. This Brachyuran is widely 

 distributed along Puget Sound, and an abundance of material 

 was available for study. Most of this was gathered in the vicinity 

 of the Puget Sound Biological Station, Friday Harbor, Washing- 

 ton, during the summers of 1915 and 1916. In the latter part of 

 June and the early portion of July, the testis of Cancer magister 

 is in the best condition for the study of spermatogenesis. At 

 these times every stage in the spermatogenesis process may be 

 found within the male gonads. 



The author worked almost exclusively with smears of the 

 testicular cells. Sectioned material was also used for comparison 

 and checking up results. The smears, however, were of greatest 

 service and virtually all the deductions and illustrations were 

 made from them. The manner in which the smears were pre- 

 pared was as follows. Small pieces of the fresh testis were 

 quickly mashed between two slides and immediately fixed in 

 Bouin's fluid for about ten minutes. The slides were then 

 washed in water until all traces of the yellowish picric acid were 

 removed. They were next stained by the iron-alum haema- 

 toxylin method, with a counterstain of acid-fuchsin. Finally, 

 they were run up in the usual manner through the alcohols into 

 xylol and when fully cleared were mounted under cover-glasses 

 with Canada balsam. Some of these preparations were unsur- 

 passed for details regarding synapsis, chromosome numbers, 



