Cytologie und Befruchtung. 263 



authors preliniinary articic. The well known work of Hacker 

 and others on Arthropoda (who describe a distribution of eniire 

 somatic chromosomes during reduction) would fall into line 

 with these results if it were shown that the transverse division 

 took place in the heterotype and not, as described, in the 

 homotype mitosis. The authors are unable to accept the re- 

 cent published view of Gregoire and Berghs that bivalent 

 chromosomes are produced in Silliim by the temporary fusion, 

 during synapsis, and later Splitting, of two spireme threads. 



The authors have especially studied in their types the 

 stages betvveen the early prophase and those in which the 

 definite chromosomes can be fully identified, for it is these 

 stages, which have been so often neglected, that give the clue to 

 the real nature of the heterotype chromosomes. They describe 

 in the prophase of the heterotype mitosis, a „first contraction 

 figure" before the „second contraction figures" or synapsis; 

 but for these and numerous other important details such as the 

 absence of a spireme filament in the pre-maiotic mitoses of 

 Periplaneta, reference must be made to the original paper. In 

 conclusion the authors review the essential features of reduction 

 and point to the strength that their observations give for „sup- 

 posing the chromosomes to be permanent structures that retain 

 their identity from one generation to another in individuals 

 composing a species". The reiation of their observations to 

 iMendelian results are briefly discussed and it is suggested that 

 the peculiarity of mosaic hybrids may perhaps be explained by 

 a special interaction of chromosomes and cytoplasm, which 

 may perhaps also help to explain the sudden sports and 

 variations met with in hybrids. In accordance with their views 

 the author suggest the term anaschistic for the premaiotic, 

 post-maiotic and one of the maiotic mitoses, as in all these the 

 chromosomes split longitudinally ; while for. the heterotype 

 (usually, if not always, the first maiotic^ mitosis they suggest 

 the term diaschistic since the Splitting is transverse as re- 

 gards the mature bivalent chromosomes. 



In the second paper which, in part, Supplements the first, 

 the authors examined somatic mitoses in the root, and the 

 heterotype and homotype mitosis in the anther, for which 

 purpose they found acetic alcohol the best fixative. The de- 

 velopment and fate of the somatic chromosomes was care- 

 fully followed and an arrangement of loops of the spireme to 

 form a definite „pole field" was observed. The number of 

 chromosomes in these nuclei is not constant but varies from 

 about twenty-six to thirty three. In the heterotype mitosis 

 there is no continuous spireme during the early stages of the 

 prophase but two „contraction figures" are to be observed (as 

 described above) and after the first is over the definite spireme 

 appears. The thread then bccomes thrown into coils which 

 are strongly „polarised and are clearly seen to be split longi- 

 tudinally". The second a synaptic contraction then occurs and 



