Nos. 451-452.] STUDIES ON THE PLANT CELL. 583 



We are now prepared to take a general survey of the proc- 

 esses of spermatogenesis to harmonize as much as possible the 

 conflicting opinions respecting the homologies of the blepharo- 

 plast. Strasburger (:oo, pp. 177-215) has critically reviewed 

 the subject and his conclusions are of great interest. He em- 

 phasizes the kinoplasmic character of the blepharoplast, whether 

 it be a differentiated region of the plasma membrane (as he 

 believes for the zoospores of Cladophora, Qidogonium, etc.) or 

 a special development in the interior of the cytoplasm (pterido- 

 phytes and gymnosperms). Strasburger thinks that all kino- 

 plasmic structures, be they centrospheres, centrqsomes or 

 blepharoplasts, hold a very close physiological relation to the 

 substance of the nucleolus and that their appearance and size is 

 largely the result of nuclear activities. Accordingly the bleph- 

 aroplast might occupy the position of a centrosome without 

 being genetically related to that structure, and in fact centro- 

 somes or centrospheres are to be considered more as products of 

 the cells' activities than as self perpetuating permanent organs. 

 There is abundant evidence that the last possibility is the fact 

 in many forms both plants and animals. Since centrosomes are 

 not found at other periods of the life history of gymnosperms 

 and pteridophytes, Strasburger concludes that the blepharo- 

 plasts cannot be genetically related (homologous) with such a 

 structure. 



Ikeno and Hirase from their earliest writings have considered 

 the blepharoplast to be a centrosome. Ikeno ('98a) held that the 

 blepharoplast corresponded with the middle piece of the animal 

 spermatozoon. Hirase ('94 and '97) although noting for Ginko 

 that the blepharoplasts did not divide and took no part in spin- 

 dle formation nevertheless called them attractive spheres. The 

 conclusions of Shaw ('98) and Belajeff ('99) for the same type 

 (Marsilia) have just been summarized and present very different 

 points of view. Belajeff beUeves that the blepharoplast of Mar- 

 silia holds the same relation to the poles of the spindles as a 

 centrosome. But Belajeff's conception of the centrosome ('99, 

 p. 204) is that of a morphological and dynamic center which 

 may or may not be easily demonstrated according to the amount 

 of stainable substance present. From these discussions it is 



