OCT ? 1902 



MAT[JI{AriON OF OVUM IN ROHINITS I']sn[Tr,ENTLTS. 177 



Maturation of the Ovum in Echinus 

 esculentus. 



By 



Tliomns II. Brycc, JII.A., M.D. 



With Plates 10—12. 



Introduction. 



The subject of the maturation of the sexual cells is a 

 thorny terrain. It can be attacked only by the highest 

 powers of the microscope, and the facts can only be 

 reached by a process of patient mental reconstruction of the 

 various phases. Historically the subject has been overlaid 

 by some brilliant but premature hypotheses, which, how- 

 ever much they may have stimulated research, have also 

 tended to foster prepossessions. The necessary stimulus 

 for research has been supplied by the hypothesis that 

 the chromatin of the nucleus is the hereditary sub- 

 stance, or, at least, the bearer from one generation to 

 another of hereditary qualities. But apart from the interest 

 connected with problems of heredity, and the meaning of 

 fertilisation, the study of the intricate details of the process 

 of maturation goes to the bottom of all our knowledge of 

 cellular morphology. The study of the maturation phe- 

 nomena in Echinus was, in the first place, taken up merely 

 with the motive of seeing some of the actual phases in the 

 most readily obtainable material. But it was soon dis- 

 covered that although the outward phases had been fre- 

 quently studied, most of the finer details of the process, as 

 seen in Echinus, were undescribed, and therefore it was con- 

 sidered worth while to make a study of the whole process. 



VOL. 40, TAUT 2. — NEW SERIES. M 



