216 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Nissen compares the milk-gland, and colostrum gland ; in the latter 

 there is no such wealth of nuclei, nor degeneration of the same. He 

 also reports the independent observation of a disruption of the 

 nucleus in the granulosa-cells of the rabbit ovum, which has also 

 been noted by Flemming. 



Accessory Nuclear Body.* — Herr G. Platner describes the origin 

 and history of the recently much discussed accessory body or 

 " Nebenkern," which has been discovered in the protoplasm of various 

 cells. His material consisted of the hermaphrodite glands of Helix, 

 which, in various stages of development, were fixed, according to 

 Flemming's method, in chrom-osmium-acetic acid for at least half 

 an hour, afterwards hardened in alcohol, imbedded in celloidin, and 

 stained with hsematoxylin or safranin. He emphasizes the importance 

 of not using animals which have been kept in captivity. 



(a) The sex-cells at first exhibit homogeneous nuclei within the 

 protoplasmic meshwork ; clear, round, intranuclear clefts and cavities 

 appear, and the contents become divided, from the centre outwards, 

 into granules. The resulting chromatin-granules are to some extent 

 connected by fine threads. The nucleus becomes gradually surrounded 

 by a narrow fringe of finely granular protoplasm, which is broader 

 at one portion, (h) At this point the " Nebenkern " appears as a 

 peculiar, distinct element, resulting from a roundish protrusion of the 

 nucleus, and possibly preformed within it. It at first consists of a 

 simple loop, but becomes more coiled and complicated, (c) Increas- 

 ing to about half the size of the nucleus, it separates from it as an 

 apparently closed coil. The spermatogonium then consists of a 

 membraneless, amoeboid cell, whose nucleus exhibits chromatin- 

 granules, filamentous meshwork, and hyaloplasma, and is surrounded 

 by a special protoplasmic envelope. The protoplasm exhibits a 

 network structure, and contains the accessory body. 



(/) The process of division is introduced by the disappearance 

 of the nuclear network ; the chromatin-granules unite in round balls, 

 most of which lie peripherally ; these balls divide repeatedly, and 

 form the microsomata. From these, persisting nucleolar elements 

 are readily distinguished by their larger size and more intense 

 staining, (g) The microsomata arrange themselves in definite rows, 

 in returning curves round an excentric pole, defined by the accessory 

 body, which has now approached and united with the nucleus. The 

 nuclear loops exhibit for a while a half-moon disposition, with the 

 concavity turned away from the " Nebenkern." (h) The latter soon 

 decreases in size, and along with the nucleolar remnants utterly 

 disappears, being apparently used up in the formation of the nuclear 

 coil, which soon afterwards loses its excentric polar position, and 

 occupies the centre. 



{i) The nuclear coil assumes the appearance of a many-rayed 

 star ; this is succeeded by the formation of an equatorial plate with 

 large granules, and by two poles with fine radiating filaments. These 

 spindle filaments extend to the equator, and without discontinuity 



* Arch. f. Mikr. Anat., xxvi. (1886) pp. 343-69 (1 pi). 



