72 4. Fortpflanzuugslehre. 



La ms a etudie les deux formes de spermatozoides de deux especes de 

 Murex (gasteropode prosobranche marin): Murex brandaris et Murex 

 trunculus. Chacune de ces especes possede des spermatozoides filiformes, 

 et des spermatozoides vermiformes (M. trunculus) ou fusiformes (M. bran- 

 daris), plus grands que les spermatozoides filiformes. Le sperme renferme 

 une quantite sensiblement egale de spermatozoides des deux sortes. 



L'auteur n'a pu determiner jusqu'ici le röle de chacune de ces formes 

 dans la fecondation et donne les resultats de ses recherches sur leur evo- 

 lution. Celle des spermatozoides filiformes ne presente rien de particulier. 

 La generation des spermatozoides vermiformes se distingue des la periode 

 d'accroissement par la plus grande taille des spermatocytes de premier ordre. 

 A la fin de la premiere division de maturation, les spermatocytes de second 

 ordre ne se separent que tres tardivement et leur noyau se fragmente souvent 

 en une demi douzaine de petits amas nucleaires. 



La seconde division de maturation est une initose pluripolare, mais 

 n'aboutit cependant qu'ä former deux spermatides, contenant chacune la moitie 

 des amas nucleaires precites. 



L'evolution des spermatozoides fusiformes (M. brandaris) est identique 

 ä celle des spermatozoides vermiformes de M. trunculus: seule l'evolution de 

 la spermatide en spermatozoide est differente. J. Duesberg (Lüttich). 



121) Scliaxel, J., Die Oogenese von Pelagia noctiluca Per. et Less. 

 mit besonderer Berücksichtigung der Chromidien und Nucleolen. 



(Zool. Anz. 35,12/13. 407—414. 3 Fig. 1910.) 

 Verf. gibt eine kurze vorläufige Schilderung der Oogenese von Pelagia 

 noctiluca und fügt einige theoretische Bemerkungen über die Beziehungen 

 zwischen Kern und Protoplasma, sowie über den Begriff des Nucleolus an. 



Gut herz (Berlin). 



122) Doncaster, L., Gametogenesis of the Gall-fly, Neuroterus len- 

 ticularis (Spathegaster baccarum). 



(Proc. Eoy. Soc. B. Vol. 82. p. SS— 112. 1910.) 

 The author describes the spermatogenesis and maturation of the egg of 

 the sexual generation, and gives some observations on the asexual generation 

 of this Hymenopteran. Somatic mitoses show 20 chromosomes in all cases 

 except in the developing nervous System of males, where only 10 are found. 

 In the spermatogenesis, 10 chromosomes appear in the spermatogonial mitoses; 

 the first spermatocyte mitosis is abortive as in the bee, while in the second 

 10 chromosomes are found and on division 10 enter each spermatid nucleus. 

 Half the spermatids contain an extranuclear body absent from the other half. 

 The maturation of the eggs of the summ er generation is irregulär, but pro- 

 bably 10 chromosomes are left in the female pronucleus, and after conjugation 

 of the pronuclei 20 are found in segmentation divisions. Experimental breed- 

 ing shows that some females of the agamic generation produce only male 

 offspring, others only female. Observations (not yet complete) on the matu- 

 ration of the parthenogenetic eggs of this generation suggest that in the eggs 

 of some females reduction of chromosome number takes place, and in others 

 not, and probably the former type of egg is male-producing, the latter female. 

 In the second part of the paper the author reviews recent work on sex- 

 determination, and suggests the hypothesis that in general females contain 

 both male and female sex-determinants, and produce male-bearing and female- 

 bearing eggs; males contain only a male sex-determinant, which however is 

 borne by only half the spermatozoa, the remainder having no sex-determinant. 



