246 BULLETIN OF THE 



central position of the nuclear structure it is to be inferred that it is either the 

 female pronucleus, or, more probably, the primary segmentation-nucleus. As 

 no description of it is given, it is not possible to say with certainty which of 

 these structures it represents. The author says (p. 90, ojj. cit.) that after the 

 yolk divides the first time he has seen that each of the resulting segments con- 

 "■ tains a small vesicle, and each of the vesicles is the centre of a slightly confused 

 radiation. At the next subsequent segmentation he did not discover the vesi- 

 cle, but only the radiation around a more or less centrally situated point, and 

 in subsequent segmentations even this radiation was no longer perceptible. 

 Even in the case of the divided yolk, there is no evidence that Derbes saw an 

 amp/waster, or any part of the spindle. 



In the same year (1847) similar phenomena were observed in the "Brut- 

 zellen," from which are produced the male elements of reproduction, — the 

 spermatozoa. Reichert ('47, pp. 120, 121, Taf. VI. Figs. 1, 23, 24) was, so far 

 as I know, the first to discover this peculiarity of the sperm-cells, which he 

 describes in the case of a Nematode, Ascaris acuminata. After the division of 

 the parent cell into two, four, or more sperm-cells, each of the latter presents 

 a very peculiar and elegant radiate appearance in its central granular portion, 

 which constitutes the principal part of the cell, and is surrounded by only a 

 narrow transparent zone without granules. The central portion of this gran- 

 ular mass is, says Reichert, more translucent than the peripheral, owing to the 

 presence of a nucleus. The centre of the nucleus, whose outline it is difficult 

 to see, is occupied by a dark round spot, the nucleolus. Immediately around 

 the latter (therefore inside the limit of Reichert's nucleus) the fat granules 

 (Fettkorperchen) look like little dots, but toward the periphery they are of 

 increasing length, so that the outermost present the appearance of little rods, 

 all pointing toward the centre of the cell. 



In the excellent studies of De Quatrefages ('48, p. 177, PI. III. Fig. 11) 

 on Hermella is contained an allusion which is probably referable to a central 

 stellate figure, whose delicate rays, however, remained undistinguished. 



Krohn ('52, pp. 314, 315) seems to have been the first to notice an am'phi- 

 aster, although he did not, after all, make special note of any connecting 

 structure between the two stars. In artificially fertilized eggs of Phallusia 

 mammillata, he observed that at the approach of each segmentation the clear 

 vesicular nucleus disappears, and that in its place there is found in each seg- 

 menting sphere a very peculiar arrangement of the yolk molecules. These 

 granules, namely, dispose themselves in thick-set streaks (dichte Streifen), 

 which appear to arise from two centres of radiation (Irradiationscentren), 

 whence they are directed outward tov^ard the lighter periphery. By the time 

 the nuclei have made their appearance within the new cleavage spheres, the 

 radial streaks have disappeared. 



The paper is without accompanying figures, but the description is so accurate 

 that it leaves no doubt as to the real nature of the rays. 



A few years later, Reichert's observations were confirmed by Meissner ('54, p. 

 209, Taf. VI. Fig. 1), who found the radial structure both in the parent cells 



