580 SUMMARY or CURRENT RESEARCHES RELATING TO 



the spiral are quite smooth, whereas the following ones are provided 

 with spines which reach as far as the outer wall of the Orhulina and 

 are there fixed firmly to it ; the several chambers communicate with 

 each other and also with the interior of the Orhulina. 



Now in an independent Glohigerina the plasmostracum is always 

 relatively thick, the perforations are close together, in short, it differs 

 in many respects from this Glohigerina-like body with which it only 

 agrees in a general similarity of form. 



It appears, therefore, that the most probable explanation is that 

 Orhulina is another instance of dimorphism among the Foraminifera 

 such as has already been shown to exist in other genera of that order 

 by the author and M. Munier-Chalmas. 



Nuclear Division in Actinosphaerium eichhornii.* — A. Gruber 

 has a note on E. Hertwig's observations on the division of the nucleus 

 of this Protozoon. In the resting nucleus Hertwig distinguishes a 

 nuclear membrane, which is best seen after the addition of reagents, 

 the nuclear substance, and the framework of achromatic substance 

 therein suspended. In the nucleolus there may be distinguished from 

 the nuclein (chromatin) paranuclein which does not take up colouring 

 matter and is much smaller in quantity ; the nucleolus varies greatly 

 in form, and may become completely broken up into two or more 

 nucleoli ; there are often as many as six or even twenty, and they 

 then form fine rods united into a rosette. 



When the nuclei begin to divide there appear two special proto- 

 plasmic cones, which lie outside the nucleus, and which, though they 

 give rise to a spindle-shaped body, are clearly not the so-called 

 nuclear spindles. The nucleolus next begins to break up, and the 

 nucleus forms a sphere filled with regularly distributed and very fine 

 granules ; these pass to the periphery, where they give rise to two 

 hyaline caps and an equatorial band of granules. In this last there 

 appears a dark band, the nuclear plate, and in the rest of the granular 

 mass fine filaments which give rise to the polar plates. These fila- 

 ments traverse the nuclear plate and so form a system which extends 

 directly from pole to pole. Lateral plates become formed which have 

 the concave side directed towards the centre of the mass, and from 

 these arise daughter-nuclei which form small, rounded, finely granular 

 bodies. 



It is clear from these observations that the nuclein in the nucleus 

 of AdinospTicerium is not a spongy framework ; the processes described 

 are intermediate between the phenomena which obtain in other 

 Protozoa on the one hand, and in animal and vegetable cells on the 

 other. As in the former, the nucleus is sharply limited at every stage 

 of division, and undergoes a biscuit-like constriction; the internal 

 changes remind one rather of what obtains in multicellular organisms. 

 The remarkable polar plates find their homologues in the nuclei of 

 the infusorian Spirochona gemmipara. Gruber ascribes the errors in 

 his own previously published observations to the imperfect preserva- 

 tion of the material with which he had to work. 



* Biol. Centralbl., iv. (1884) pp. 233-5. 



