110 Miscellaneous, 



ciliated, •whereby an active movement is imparted to the intestinal 

 coutents. 



The oral opening, which is not quite terminal in position, is over- 

 topped by one cell in front. The cirri, which I have previously 

 mentioned, are borne upon this cell, as well as upon the others sur- 

 rounding tlie mouth. These cells are therefore well diti'erentiated 

 from the remainder, so that altogether we have to distinguish three 

 different kinds of cells. 



The limits of each individual cell are distinctly visible, and almost 

 in the centre of each there is a large roundish nucleus, containing 

 several smaller nucleoli, which may usually be made out even in 

 the living animal. The remainder of the contents of the cell are of 

 a finely granular nature, though it is impossible to determine with 

 certainty whether the nutritive contents of the intestine are received 

 into the cells in solid form. I am inclined to believe that this is 

 not the case. A lew globules of fat, on the other hand, are dis- 

 cernible in most of the cells. 



I frequentl)' found these animals of different sizes. Growth 

 simply results from the reduplication of cells by division, which 

 takes place in such a way that the nucleus first becomes more homo- 

 geneous, since the nucleoli disappear from view. The nucleus, 

 which has become elongated, then constricts, as does also the cell 

 almost at the same time, whereupon complete division ensues, the 

 nuclei first separating from one another and then assuming a 

 rounded form. They subsequently become clear again and exhibit 

 the nucleoli. Whether during this apparently direct division of the 

 nucleus morphological changes take place in its interior it was 

 impossible to determine in living specimens. Similarly it has not 

 yet been possible to decide whether a true nuclear membrane is 

 present, and, if so, how it behaves during the division. At aU 

 events, in observing the process no change can be detected at the 

 margin of the nucleus. 



Unfoi'tunately I have not yet succeeded in killing the animals 

 successfully, as on the addition of foreign matters they at unce 

 melt away exactly like Infusoria, since the cells sci)arate from one 

 another, assuming a spherical shape, and then flatten out after losing 

 their cilia. 



With regard to reproduction, two methods appear to exist. In 

 the first place, in large individuals, a transverse division takes place, 

 which vividly recalls the similar process in CaUiuda &c. The cells 

 of the middle region usually first divide ; a constriction of the animal 

 then sets in at this spot at right angles to the longitudinal axis, 

 while a new mouth is formed in the i)Osterior division, since a few 

 cells upon the ventral surface separate from one another and give 

 rise to an opening, at the same time producing stronger cilia. Upon 

 this the whole is constricted oft', and the two animals are set free 

 and swim away. 



Besides this, however, we find conjuifiidon, with subsequent 

 cncystnienl. Two individuals apply themselves together by their 

 ventral surfaces, and discontinue the movement of their cilia. They 

 tlien become shortened and rounded into a common spherical mass, 



