96 NOTES AND MEMORANDA. 



iianow isthmus, occupying one of the mutual communica- 

 tions. One portion of such a nucleus might be sometimes 

 very small as compared to the other, so much so as to he 

 reduced to a mere tip. From this circumstance the author 

 regards a passage of the nucleus from one chamber to an- 

 other by means of the connecting canals as probable, and 

 the disturbance of the normally globular figure to be due to 

 the constriction caused by the narrowness of the passage. 



The author found afterwards a similar nucleus m a 

 Rotalina. 



Whilst admitting that the foregoing observations do not 

 as yet prove all Foraminifera to be nucleated, the author 

 still would suggest the likelihood that they really are so. 

 From the fact that the whole of the soft body of a many- 

 chambered Folystomella or Rotalina normally has but a 

 single nucleus, it follows that the whole animal has but the 

 value of a single cell, and the old question as to whether the 

 Polythalamia are to be regarded as single animals or colonies 

 of animals is disposed of, as the Foraminifera at large 

 (admitting possible exceptions) must be regarded as uni- 

 cellular animals. 



Subsequent to his study of the freshwater Monothalmia, 

 Hertwig turned his attention to the marine Mono- and Poly- 

 thalamia, with the view of investigating their probable rela- 

 tions to the former. Both groups naturally appeared to him 

 to possess, on the whole, great affinity, whilst certain of the 

 characters relied upon by most naturalists in recent times, as 

 calling for their separation, seemed to him not to possess so 

 broad a systematic importance, nor to be so comprehensive 

 as was usually assumed, such as the characters of the pseu- 

 dopodia, or the distinction between non-contractile vacuoles 

 and contractile vesicles. He had, therefore, come to the 

 conclusion that the only character left to systematically- 

 separate the freshwater Monothalamia from the Foraminifera 

 was the absence of a nucleus in the latter and the presence 

 of this important structure in the former. For if, as had 

 been generally assumed, the Foraminifera represented only 

 an undifferentiated, non-nucleated, test-bearing protoj^lasmic 

 mass, then, in a histological point of view, they could only 

 be regarded as cytodes, whilst the freshwater forms would 

 possess the morphological value of one or more cells ; the 

 Foraminifera would, therefore, come more close to HaeckePs 

 Monera. 



Max Schultzc was the only observer who had afforded us 

 a knowledge of the structure of the soft body, the researches 



