750 SUMMARY OF CURRENT RESEARCnES RELATENQ TO 



probable that it has respiratory and circulatory functions, while its con- 

 tuinoil litjuitl may possibly be of a nutrient nature. This jutlgnicnt is 

 chiefly based on the fact that in no case has the autlior been able to 

 observe a direct communication with the exterior. He regards it as 

 certain that the liquid which is driven out by the vacuole does not quit 

 the protoplasmic body, but is distributed throughout it. A confirmatory 

 fact is to bo found in the observation that in the i)rotoplasm droplets 

 appear which fuse to form the first sign of the contractile vacuole. As 

 the droplets leave the vacuole they grow smaller and smaller till they 

 are, at last, invisible. 



Further Observations on Multinuclear Infusoria.* — Prof. A. 

 Grubcr has made some further observations on multinuclear Infusoria. 

 He finds that there are a considerable number of marine Infusoria, 

 holotrichous, and, especially, hypotrichous forms, in which numerous, 

 sometimes hundreds of nuclei are scattered in the plasma. The fact 

 that these bodies show, when dividing, the well-known striated structure, 

 proves that they are really nuclei. When a division is about to take 

 place they fuse into a single mass ; but this may again break up before 

 the daughter-individuals have separated, and so in each of these there 

 may be a large number of nuclei. 



It is difiicult to say what this multinuclear condition means ; it is 

 possible that it is an advantage against injuries, for each separate piece 

 would contain at least a nucleus or a paranucleus, and so be capable of 

 regeneration ; such pieces are, also, capable of growing up into comi)leto 

 individuals, while non-nucleated i)ieces do not last long. In support of 

 this supposition it should be noted that these multinuclear Infusoria are 

 all very soft and changeable in form ; some also are greatly elongated, 

 and so frequently exposed to injuries. The multinuclear fresh-water 

 Infutoria, Loxodes rostrum, is also a fragile organism, and here too the 

 numerous nuclei have perhaj^s the same significance. 



In Opalina ranarum the large number of nuclei is connected with the 

 mode of reproduction which, as is well known, consists in a number of 

 rapidly succeeding divisions, or what might be called a breaking uj) of 

 the body into a number of pieces, each of which has one or more nuclei. 



The case of Holosticha scutellam shows us that we are not justified in 

 concluding that a substance is absent because we cannot see it at once 

 with the best of our optical instruments. The paranuclei are here so 

 small, owing to repeated division, that they cannot be seen by our eyes. 

 In Choenia teres and in Trachelocerca the nuclei themselves are so small 

 that they only appear as fine granulations. If the author's idea that the 

 nucleus is the seat of the histogenetic plasma, and the paranucleus that 

 of the idioplasma (germ-plasma) be correct, Holosticha scutellum affords 

 us a proof that the latter, although of material nature, may be removed 

 from our perception, in consequence of repeated divisions. This is 

 generally the case in the metazoic cell, although at certain times of 

 cell-life it may be visible to us. In the process of division in Holosticha 

 the nuclear mass, which is at first single, becomes broken up into pieces, 

 not in any chance way, but by a succession of nuclear divisions ; we 

 must suppose that the same happens to the substance of the para- 

 nucleus, recognizing that we have to do with values which are so small 

 that we cannot perceive them with our present means of research. What 



* Ber. Nat. Gesell. Freiburg i. 13., iii. (18SS) pp. .57-09 (2 pis.). 



