THE VITAL PHENOMENA OF THE CELL 243 



apart, is connected by means of two spindles to the remaining 

 portion of the figure, which forms a triaster. Of these two 

 spindles one is only faintly and imperfectly developed, and is 

 further remarkable for the small number of its nuclear segments. 

 Apparently it would never have made its appearance if radiation 

 x had been at a somewhat greater distance from radiation y. 



Nuclear figures with three, four or more poles (triaster, tetraster, 

 poly aster, multipolar mitoses), have been frequently observed by 

 pathological anatomists in tissues altered by disease (Arnold, 

 Hansemann, Schottlander, Cornil, Denys, etc., VI. 1, 10, 11, 25, 

 67) ; they occur with especial frequency in malignant tumours, 

 such as carcinoma, and resemble to a remarkable extent those 

 produced artificially in egg-cells, such as are represented in Figs. 

 129 to 131. Apparently the cause for the abnormal appear- 

 ances may be traced to chemical stimuli. Thus Schottlander 

 (YI. 67) was able to excite pathological nuclear division in the 

 endothelium of Descemet's membrane by cauterising the trans- 

 parent cornea of the Frog's eye with chloride of zinc solution of a 

 certain strength, and thus inducing inflammation. It is remarkable 

 how much the number of nuclear segments may vary in individual 

 spindles. For instance, Schottlander found as many as twelve 

 segments in some spindles, and in others only six or even three ; 

 the same was observed in Echinoderm eggs. 



Further, multipolar nuclear figures may apparently be due to 

 other causes, about Avhich at present extremely little is known to 

 us. For instance, a very common cause is the presence of several 

 nuclei in one cell. Such a condition can be easily produced 

 artificially by injuring egg-cells in some suitable way, and by 

 subsequently fertilising them (Fol VI. 19 b ; Hertwig VI. 30 a, 

 32, 33, 38). Under these circumstances instead of one single 

 spermatozoon entering in the usual manner, two, three, or more 

 make their way into the yolk. The consequence of this kind of 

 over-fertilisation (polyspermia) is the formation of several sperm 

 nuclei, corresponding in number to the spermatozoa which entered. 

 Some of these approach the egg nucleus, and since each of them 

 has brought a centrosome with it into the egg, a corresponding 

 number of pole radiations develop around the egg nucleus. And 

 thus, according to the number of spermatozoa, the egg nucleus 

 becomes transformed into a nuclear division figui'e with three, four, 

 or more radiations. 



Further, those sperm nuclei which are not in contact with the 



