34 Dr. F. Blochmann on the 



formed shell of the individual produced bj copulation ex- 

 ceeded the normal measurement by about 20 /i in each 

 dimension. 



X 300. 



In the large animal III. a nucleus was visible in the usual 

 position. As to the behaviour of the two nuclei of the copu- 

 lating animals I. and II., I could make no observations owing 

 to the nature of the case. The most natural supposition seems 

 to me to be that the two nuclei were fused together. The 

 large individual crept about briskly in the drop for several 

 days and was finally encysted on June 2. The two other 

 conjugated animals in the same preparation separated again 

 from each other, and one of them divided in the normal 

 manner. 



In this instance, therefore, there can be no doubt that actual 

 copulation occurs in Eugli/pha, only it seems to be compara- 

 tively rare ; and hence its exact observation must depend 

 upon favourable circumstances, which, considering the import- 

 ance of the matter, is much to be regretted. 



When through recent investigations, and especially by 

 Gruber's memoirs, the process of division in the freshwater 

 Monothalamia was elucidated in all essential particulars, it 

 appeared only tdo natural that there should be a great ten- 

 dency to assume, as indeed had even previously been done by 

 Hertwig and Lesser *, that all statements as to the copulation 

 and conjugation of the shelled freshwater Rhizopods were 

 founded upon such divisional stages misunderstood. In many 

 cases this might probably apply, in some perhaps not. Of 

 course from the figures and descriptions it will be difficult or 

 even impossible in special cases to decide in favour of one or 



* " Ueber RLizopoden und denselbeu nahestehenden Organismen/' in 

 Arch, fiir inikr. Auat. Bd. x. Suppl. pp. 35-243 (1879). 



