314 Fortpflanzung. 



tamorphosis. In: Quart, Journ. Micr. Sc, Bd. 58, Heft 3, S. 523 — 552, 



3 pl., 1913. 



Details are given of the metliods used in producing artificial parthenogene- 

 ais by Loeb's andDelage's methods, and by a combined method (butyric acid 

 followed by sucrose and tannic acid) wliich was more successful than the others. 

 The parthenogenetic larvae are distinguishable by the greater length of the 

 arms and other minor features in the early stages, and by their slower rate of 

 growth later. Parthenogenetic larvae were reared through the metamorphosis to 

 young echini, but the slow rate of development usually causes death from star- 

 yation at the period when the mouth and anus of the young urchin are still 

 closed. Doncaster (Cambridge). 



1016) Debaisieux, G. (Louvain, Belgien, University), The Experimental 

 Hybridisation of Echinus miliaris, E. esculentus and E. acutus. In: 

 Quart. Journ. Microscop. Science, Bd. 58, Heft 2, S. 325—335, 1 pL, 1912. 

 The author has repeated the experiments of Shearer, De Morgan and 

 Fuchs on these species (see the summary of their work in this number of this 

 Zentralblatt), and has arrived at somewhat different results. He considered 

 Chief ly the following three characters. (l) The posterior epaulettes, present in 

 acutus and esculentus, absent in miliaris. (2) The posterior pedicellaria, present 

 in acutus and esculentus, absent in miliaris. (3) The green pigment, present in 

 miliaris, absent in acutus and esculentus. The four possible hybrids with miliaris 

 (miliaris $ X acutus d" and esculentus d"; acutus 5 and esculentus 5 X miliaris <S) 

 were obtained. In all four hybrids the posterior epaulettes were present, but 

 not always so perfect as in pure acutus or esculentus. The posterior pedicellaria 

 was present in all the crosses with the possible exception of miliaris $ X escu- 

 lentus cT. There was some irregularity, and in some larvae it was absent. The 

 green pigment was never found in any of the hybrids. The author therefere 

 concludes that the appearance or non-appearance of a character does not depend 

 on whether it is transmitted by the female or the male parent, but that some 

 characters are dominant when transmitted by either parent, others (e. g. green 

 pigment) recessive. The dominance of dominant characters is however subject to 

 Yariation, and may be incomplete. Doncaster (Cambridge). 



1017) Doncaster, L. and Gray, J. (Cambridge, University), Cytological 

 Observations on the Early stages of Segmentation of Echinus 

 Hybrids. In: Quart. Journ. Micr. Sc, Bd. 58, Heft 3, S. 483—510, 2 pL, 1912. 



In the cross E. esculentus $ X acutus c? the segmentation is normal. In the 

 converse cross acutus 5 X esculentus S', as the nuclear membrane disappears in 

 the first segmentation division, several chromosomes (2 — 12), swell up and be- 

 come vesicular. The chromosome may be entirely converted into a vesicle, or 

 may produce and throw off a vesicle and subsequently behave normally. The 

 vesicles may be included in the daughter nuclei, but are more commonly left on 

 the spindle and eliminated. The chromosome number is thus reduced from 38 

 to 31 — 37. In the second segmentation division, vesicles are again produced, 

 but probably from parts of chromosomes, so that no further numerical reduction 

 is brought about. 



In the cross acutus 5 X miliaris c? a small number of small vesicles is com- 

 monly produced, and some chromosomes, which do not become corapletely vesi- 

 cular, probably fail to divide. The later segmentation divisions are apparently 

 normal. In esculentus $ X miliaris c? no vesicle-formation was observed. In mi- 



