DESCRIPTION OF 'M <TS. 



tail, :tnl to know their diilVivnt chemical :in.l ropertics. The view 



;-y K. ii. i. IK 1:1:. th.-it ordinarily the seminal filaments were the 

 metamorphosed anil elongated nuclei of tin- seminal cells, underwent a m< 



. :iiL, r to tin- researches <f !,.\ v 'he head of the 



seminal tilamei.' -n the nucleus, t he tail, on the contrary, from the 



protoplasm of the spermat id. Finally I-'I.I:.M \IIN<; i.n.ujiit f'(.r\vanl convincing 

 proof that it is only the chromatin of the nuc., 



the head of the seminal filament. Important inve>: ipit i'-n* con'''-niiii the 

 >l>ment of the seminal filaments in various animals have recently been 

 madel>\ VAN BBVBDHI irJULIir, I'I.ATNI:I:. HI.I:M\ 'hers. 



SUMMARY. 



The most important results of this chapter may be briefly sum- 

 marised as follows : 



1. Male and female sexual products are simple cells. 



_. The seminal filaments are comparable to flagellate cells. T 

 ;uv usually composed of three portions, head, middle piece, and 

 contractile filament. 



3. The seminal filament i> developed out of a single cell, the 

 sprnnatid; the head, and probably also the middle piece, from the 

 nucleus ; the contractile filament from the protoplasm. 



4. The egg-cell consists of egg-plasm and yolk-particles, which are 

 . material (deutoplasin), imbedded in it. 



5. The quantity and distribution of the deutoplasm in thee^-cell 

 is subject to great variation, and exercises the greatest influence on 

 the course of the first processes of development. 



(a) The deutoplasm is small in amount, and uniformly dis- 



tributed in the egg-plasm. 



(b) The deutoplasm is present in tjuantity, and, in 



consequence of unequal distribution, is more densely 

 cumulated either at one pole of the egg or in its middle. 

 (Polar and central deutoplasm.) 



(c) In <\L r j_ r s with polar deutoplasm (eggs with polar ditl' ivntia- 



tion) the pole with more abundant deutoplasmic contents 

 is designated as the vegetative, the opj>osite one as the 

 animal pole. 



(</) In the case of eggs with p.lar differentiation, the more 

 abundant protoplasm of the animal pole may be sharply 

 differentiated as germ-disc (formative yolk) from the 

 portion which is richer in deutoplasm (nutritive yolk). 

 The developmental processes take place only in the 

 formative yolk, while the nutritive yolk remains on the 

 whole passive. 



