Dr. L. Plate on Asellicola dia-Itata. 211 



tj' 



divide into a central and a cortical layer, but presents the same 

 constitution throughout. The nucleus (N) has an elongated 

 sausage-like shape and is often furnished with hemispherical 

 projections and small irregular side-branches. Not unfre- 

 quently it has the outlines of an irregular cross. Externally 

 it is bounded by a delicate nuclear membrane and in the 

 interior we observe a fine granulation as the expression of a 

 very close meshwork. There are no nucleoli ; but the Aselli- 

 colce frequently possess those little round balls which stain 

 strongly with colouring-materials (fig. 4, ti) such as I have 

 previously described as " Tinctinkorper " in Dendrocometes. 

 These are evidently assimilation-products of some kind which 

 have nothing to do with the nucleus, for they are subject to 

 considerable variations in their number and size. In well- 

 fed animals containing numerous fat-drops we frequently find 

 as many as thirty scattered through the interior of the cell ; 

 in other specimens, again, they are entirely wanting. That 

 they are not to be identified with the nucleoli of the Ciliata 

 appears with certainty from the circumstance that they 

 undergo no alteration during conjugation. 



In Asellicola digitata, as in Dendrocometes , there are also 

 not unfrequently green or yellowish-green bodies of O'OOJ- 

 0'005 millira. in diameter, which at the first glance greatly 

 remind us of chloropliyll. Here again I have convinced 

 myself that the globules are formed by the Acineta itself, and 

 therefore do not merely get into the animal with the food ; 

 for in the first place they are destitute of any cellular struc- 

 ture, so that all confusion with unicellular Algge is excluded, 

 and, secondly, they remain unaltered in the plasma often for 

 hours ; they may often be seen in specimens which have 

 retracted all their tentacles, a process which occupies con- 

 siderable time. As the Protozoa universally rapidly digest 

 and at the same time decolorize true chlorophyll-grains wliich 

 are taken up with the food, there only remains one interpre- 

 tation, according to which these green structures represent 

 assimilation-products of some kind. The green colouring- 

 matter can be extracted by alcohol, and then there remain 

 granules'which cannot be distinguished from the other shining 

 granules of the cell. 



The contractile vacuole of Asellicola digitata (fig. 4, cv.) 

 is placed near the lower margin of one of the lateral poles of 

 the body. It opens, as in Dendrocometes paradoxus^ directly 

 outwards by a small duct, and contracts so that the tiuid 

 which has collected in it must be pressed out through this 

 tubule. The intervals of time at which the pulsations follow 

 one another are very various and depend apparently upon the 



