No. 2.] THE SPERMATOGENESIS OF LUMBRICUS. 273 



The state of differentiation of the sperm blastophore is a 

 superficial guide to differences in age of the cells, but can be 

 depended upon only to mark the latest stages, where spermatids 

 and blastophores are connected by the merest traces of proto- 

 plasm. 



I desire to express my gratitude to Professor Wilson for his 

 continued encouragement and advice. Also I take this oppor- 

 tunity to express my indebtedness to the American Associa- 

 tion for the Advancement of Science for the use of their In- 

 vestigators' Room at the Marine Biological Laboratory during 

 the season of 1894. 



I. Methods, 



My best results have been obtained by killing with Her- 

 mann's fluid, a solution consisting of fifteen volumes of plati- 

 num chloride one per cent, two volumes of osmic acid two per 

 cent, and one volume of glacial acetic acid. Specimens in 

 various stages of sexual development are selected, and cleaned 

 with filter paper in the usual manner. Segments 9 to 13 inclu- 

 sive are then cut from the worms and left in the Hermann 

 solution for not more than thirty minutes. By this method sec- 

 tions of the testes and seminal vesicles can be obtained {71 situ. 

 When merely the contents of the seminal vesicles are desired a 

 simple and much more satisfactory method is to cut away from 

 the dorsal side the entire alimentary tract together with the 

 calciferous glands, leaving the large seminal vesicles exposed. 

 The sections may then be stained on the slide. For staining, 

 my best results were gained by the use of Heidenhain's iron 

 haematoxylin, and the safranin, gentian violet, and orange 

 triple stain of Flemming. Good results were also obtained by 

 Mayer's haemacalcium and the Biondi-Ehrlich mixture. 



The above methods involve the use of heat and imbedding 

 in paraffine, a process which almost invariably shrinks the tis- 

 sues of Lnmbricus. To avoid this difficulty I found it advan- 

 tageous to use teased specimens. The method is as follows : 

 the large seminal vesicles of sexually mature worms are 

 selected and teased in a watch crystal containing, usually, the 

 killing agent. The teasing is easily accomplished with fine 



