No. 2.] THE ECHINODERM SPERMATOZOON. 24 1 



d. One per cent aqueous solution of gentian-violet under 

 cover-glass : nucleus deeply stained, mitosome and centrosome 

 slightly. 



e. Stain strongly in gentian-violet ; decolorize in water hav- 

 ing a trace of acetic : only the nucleus is stained. 



/. Gentian-violet, 24 hours ; decolorize in acid absolute 

 alcohol ; stain 3-10 minutes with eosin in absolute alcohol : 

 nucleus purple, mitosome and centrosome pink. 



g. With very dilute Delafield's haematoxylin only the 

 nucleus stains. 



8. Fix in platinum chloride 0.3% for 24 hours. 



a. Stain in aqueous solution of safranin : only nucleus stains. 



b. Run dilute aqueous solution of dahlia under the cover- 

 glass : nucleus stains red ; mitosome and centrosome violet. 



C. The material for sectioning is best killed in Flemming's 

 or Hermann's fluid. Sections in paraffin of different thickness 

 (i-io/i) were studied. 



Historical Summary. 



The history of the discovery of spermatozoa by Ham and 

 Leeuwenhoek, and the original belief that they were animal- 

 cules — the spermatic animalcules, by some investigators re- 

 garded as infusoria, by others as allied to cercaria — need not 

 be entered into here. It was not until about 1841 that the 

 first important generalization upon spermatogenesis was made. 

 Kolliker discovered that the " Spermfadern," as he called them 

 — substituting this term for the hitherto adopted " Samen- 

 thierchen " — developed from the internal wall of the testis, 

 and hence were metamorphosed cells (15). Later (1847) he 

 described the spermatozoa as formed not from a single entire 

 cell, but only from its nucleus, or even only a part of its 

 nucleus. 



As the result of a third work he decided that the 

 spermatozoon is formed purely and simply of nuclear matter ; 

 that the entire nucleus of the germinal epithelium cell became 

 transformed into the spermatozoon. This nucleus, at first 



