90 



INTRODUCTION TO CYTOLOGY 



jeff (1888), Guignard (1889), and Schottlander (1893), give but little 

 information concerning \\\r developmenl of the blepharoplast. Our more 

 definite knowledge of this subject dates from 1897, when Bela jeff published 

 three short papers. In the first of these (1897a) it was stated that the 

 fern spermatozoid consists of a thread-shaped nucleus and a plasma band. 

 with a great many cilia growing out from the latter. In the plasma band 

 is enclosed a thin thread which arises by the elongation of a small body 

 seen in the spermatid. In the second paper (18976) the blepharoplast of 

 Equisi turn was first described as a crescent-shaped body lying against the 

 nucleus of the spermatid; this body stretches out to form the cilia-bearing 

 thread. The third contribution (1897c) is a short account of the trans- 

 formation of the spermatid into the spermatozoid in Cham, Equisetum, 



Fig. 30. — Spermatogenesis in Equisetum arvense, showing behavior of blepharoplast 

 (centrosome) in last spermatogenous mitosis and in transformation of spermatid into sper- 

 matozoid. X 1900. (After Sharp, 1912.) 



and ferns. In all these forms a small body elongates to form a thread 

 upon which small swellings arise and grow out into cilia. In a comparison 

 with animal spermatogenesis Belajeff here homologized the blepharoplast, 

 the thread to which it elongates, and the cilia of the plant, with the 

 centrosome, middle piece, and tail (perhaps only the axial filament), 

 respectively, of the animal. In the following year (1898) he figured the 

 details made out in Gymnogramme and Equisetum. In Gymnogramme the 

 two blepharoplasts appear at opposite sides of the nucleus in the spermatid 

 mother-cell, whereas in Equisetum a single blepharoplast is first figured 

 lying close to the nucleus of the spermatid. More recently it has been 

 shown (Sharp 1912) that the blepharoplast of Equisetum (Fig. 30) appears 

 first in the cells of the penultimate generation; there it divides to two 

 which separate and establish between them the achromatic figure after 

 the manner of animal centrosomes. At the close of mitosis the blepharo- 



