46 MARCUS M. HARTOG. 
The following schema contrasts the conjugation of the 
Desmid Closterium, and of a Ciliate. 
The zygote of the Closterium is totally different from the 
gametes, whose structure can only be obtained afresh by a 
very complex reorganisation and after protracted rest. The 
Ciliate, on the contrary, carries away from conjugation its 
cytoplast with all its complexity retained, and yet has a 
nucleus of the same “ form” as that of the zygote of Clos- 
terium. The process then seems to involve the suppression 
of formation of proper gametes, in order to gain the advantage 
of the retention of the cytoplasmic body unchanged. 
iii 
—_—_—— 
~ 
i ii 
ee an 
ram (aa 
Hig ic gh 
( \ \ 
iH \ 1 i 
A es 
1 
N Ve ay 
= 
———— 
aan CuK 
\ 
H 
1 
{ Neawe 
{ 
U 
\ i 4 KY 
= 
DAG 
Fic. 7.—Comparisons of three stages of the processes immediately leading 
up to conjugation in Closterium (A) and Parameecium (B). In each case 
two zygote-nuclei of the value (N’ + M' = Z) are formed, but the cyto- 
plasts are unchanged in B, and totally altered in A. 
Having found a key to the final processes of conjugation we 
can step back, and consider the first two mitoses with the form- 
ation of the rejection-nuclei. We may fairly regard these 
also as attempts to form a plurality of gametes comparable 
with the processes observed in certain Fucacez, the position 
in the cytoplast determining which nuclei shall be rejected. 
Possibly, too, the failing energies of the meganucleus at this 
stage are insufficient to determine the division of the cytoplast; 
