ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



715 



within the nucleus of the spermatids, but later breaks up into fine 

 granules in the same manner as the autosomes. 



In Dissosteira Carolina, the nebenkern is not derived directly from 

 the remains of the spindle fibres, but is probably formed chiefly from 

 the mitochondrion. The axial filament is from the first connected with 

 a distinct centrosome, which is applied to the exterior of the nuclear 

 membrane. As the spermatid elongates, the nebenkern becomes con- 

 verted into an envelope surrounding the axial filament. The head of 

 the mature spermatozoon is formed entirely from the nucleus ; the 

 centrosome forms the greater part of the middle piece, while the tail is 

 composed of a central fibre, derived from the axial filament and 

 nebenkern, surrounded by a cytoplasmic envelope. 



In Steiroxt/s trilinedta the axial filament is apparently not at first 

 connected with a centrosome, which appears in the usual position only 

 when the axial filament is well developed. The axial filament is from 

 the first surrounded by an envelope of doubtful origin, denser than the 

 surrounding cytoplasm. The nebenkern migrates round the nucleus, 

 and becomes applied to its anterior end. The head of the mature 

 spermatozoon is formed from the nucleus and the nebenkern, the latter 

 developing into the acrosome ; the middle piece is formed chiefly from 

 the centrosome, which divides into four parts ; while the tail is composed 

 of the central fibre derived in part from the axial filament surrounded 

 by a cytoplasmic envelope. 



In no case is there evidence that the monosome is extruded from the 

 nucleus, nor is there evidence that the spermatids degenerate, except 

 in rare instances. Therefore, the mature spermatozoa must be dimor- 

 phic with respect to chromatic content, although there are no visible 

 differences either in form or volume between the two types. Throughout 

 the entire history of the germ-cells there is strong evidence for the 

 individuality of the chromosomes. 



Oviposition in Aphelinus.* — P. Marchal describes in some detail 

 the way in which Aphelinus mytilaspis, a very minute Chalcidid, lays its 

 eggs in Aspidiotus — carefully exploring the body of its victim to find a 

 suitable place, making a wound and licking it many times in succession, 

 and showing an "individual interest" and variety in its behaviour 

 which makes the whole performance much more than instinctive routine. 



Gynandromorphs of Anergates atratulus.f — G. Adlerz describes 

 two individuals, predominantly like males, but with wings, and on the 

 right side with several feminine characters. One of them tried to pair 

 with females, while males tried to pair with it. On the left side there 

 was a well-developed male apparatus, and internally a seminal vesicle 

 with an associated vas deferens. On the right side there were no 

 internal organs, and the external parts were imperfect. The right tibia 

 and tarsus were feminine in character, the left masculine. There was 

 no trace of female gonads or of poison gland. 



* Comptes Rendus, cxlviii. (1909) pp. 1223-5. 

 t Arkiv f. Zool., v. (1909) No. 2. pp. 1-6 (1 pi.). 



