i 1111: SBZ1 \i. PBODt (T8. 19 



and which constitute tin- down- thai i> L'iv.-n by the mat- 



ni.Mn ti tin- developing germ on Thereupon tin- whole 



I in one or sever: il M coiidary egg-membranes, :nnl now 



nut. s the compound egg, in which, bowever, thr developmental 

 pr. >ce>s s niMiiifist themselvt s exchiMVely on the simple germ cell ; 

 it is that alone which is J' rtilisecl and segments, while tin- yolk < IK 

 gradually degenerate and are employed as nutritive matt-rial. 'I 

 in this ease also, upon closer examination, tin- general la\v, that the 



ndent organism tab s its origin from a single cell of the maternal 

 1 ody. Mill, is no exception. 



2. The Seminal Filaments. 



Tn contrast with eggs, which are the largest cells of the animal 

 body. the sperm-cells or sperm-filaments (spermatozoa) are the 

 smallest elementary parts; they are accumulated in great multitudes 

 in the seminal fluid of the male, but can be recog- 

 nised in it only by the aid of high magnification, 



~ * 



being, for the most part, slender motile filament.-. 

 Inasmuch as every cell consists of at least two 

 namely, nucleus and protoplasm, we must 

 look for the>e parts in this case also. We shall 

 take for description the spermatozoa of Man. 



In Man the seminal filaments (fig. 9) are about 

 <Hir> mm. long. One may distinguish as head (k) 

 a short but thick region, which marks the anterior 

 end, as tail a long thread-like appendage (s), and F 



matozoa of Man, 

 betwtell the two a SO-Called middle piece (m). teen in two dif- 



The head ( /, ) has the form of an oval plate, ff P osition8 - 



consists of a 



which is slightly excavated >n both Mirt head (A-), a mid- 



and is somewhat thinner toward the anterior end. Sujjj* ' ni)l and 

 Seen from the side (/?) it presents a certain re- 



semblance to a flattened pear. Chemically eon>idered, it consists of 



nuclear sulMaiuv (nuclein 01- chroinalin). as microchemical reac' 

 >how. To the head i* unittd. l>v u,ean> of a >ln>rt part callr., 

 middle piece (in), the long thread-like appendage (s), which is com- 



,1 of proti^>la>m, mid i> hot compared to a ilagellum, bee: 

 like the lntte-r.it executes peculiar .-erpentine motions in virtue of 

 its contractile properties. j'.y im>an> of th-e moti. n- the sper- 

 inato/.oJin move.- forwards in the >eininal tluid with e n-iderable 

 velocity. 



