and Reproduction of the Polythalamia. 319 



the cells to coalesce into a larger mass of protoplasm, in which 

 then only the number of the persistent nuclei may perhaps in- 

 dicate the origin of the mass from cells. In some forms it is in 

 the cortical part of the body that such a mass occurs ; these are 

 Rhizopoda, among which, according to the important investi- 

 gations of Johann Miiller, and especially the recent ones of 

 E. Haeckel, with which I am chiefly acquainted by oral commu- 

 nication, the RadiolaricE, Acanthometra, and Polycystime must 

 occupy the highest place, inasmuch as in them cells actually 

 persist in the manner above indicated. In other Protozoa a 

 stratified layer of more or less independent cells might exist ex- 

 ternally, as in the Infusoria, whilst internally the body is filled 

 with protoplasm not capable of being resolved into cells, and 

 produced by the coalescence of cells. As such I indicate the 

 soft central substance of the Infusoria into which the morsels 

 of food are passed. It is the softest part of the body of the In- 

 fusorium, but belongs to it just as much as the cortical substance, 

 and cannot bear the name of " chyme,^* which Lachmann has 

 applied to it. 



From this point of view I might proceed to the explanation of 

 the organization of the Infusoria, and I am convinced that we 

 may thus arrive at a satisfactory solution of this difficult matter j 

 but I must call attention to one thing which is not unimportant, 

 namely that the theory also admits the assumption of unicellular 

 Infusoria. For one cell may acquire cilia on its surface; one 

 cell may contain a harder cortical layer and a soft medullary 

 substance, with vacuoles, nucleus, the most various corpuscles, 

 pigment-vesicles, &c. In a single cell, as is shown by the young 

 cells of muscular fibre, the periphery of the protoplasm may 

 be converted into true muscle- substance, whilst the centre of 

 the cell is still occupied by ordinary protoplasm. Whether a 

 so-called contractile vesicle may be produced in the protoplasm 

 of a single cell, certainly requires further investigation, but it 

 does not appear improbable. Lastly, that a cell (therefore in this 

 case a mass of protoplasm with a hardened and ciliated cortical 

 layer) may be destitute of the hardened layer and cilia at one or 

 two spots of its surface, or possess a " mouth '^ from which solid 

 matters are pressed into the innermost, soft, protoplasmic mass, 

 and an " anus " for the evacuation of the same, is a point of which 

 I have already spoken above, and 1 believe that the possibility of 

 such an occurrence must be admitted. 



In conclusion, the new observation already mentioned, upon 

 the reproduction of a Polythalamion of the family Rotalida, may 

 here find a place. 



In a bottle with sea-water and a little sand, which had been 

 collected from a depth of about 30 feet off Heligoland and well 



