168 



the right half (pars dextra a. p. a.) has been depressed on to axis 

 and become completely fused to it (Figs. 2 and 3), excepting in the 

 region of the intervertebral foramen. 



The left half of the posterior arch of the atlas thus remains 

 suspended as a horizontal bar with a free, i. e. unattached, extremity 

 (Fig. 2). 



The superior articular surfaces of the atlas are not concave, as 

 is usually the case: they form a flat (sloping) surface on which the 

 cranium can rotate and thus, in some measure, compensate for the 

 loss of rotatory movement, which would otherwise have been the result 

 of such an immovable union of axis and atlas as this case presents. 



Nachdruck verboten. 



Spermatogenesis ot the Honey Bee (Apis mellifica). 



Correction. 

 By L. DoNCASTEK, M. A. 



In the "Anat. Anz." (Bd. 29, 1906, p. 490) I published a note on 

 the spermatogenesis of the Bee. I described in the final maturation 

 division eight double chromosomes in the equatorial plate of the spindle, 

 each of which divided so that eight single chromosomes passed to 

 either end. A fresh examination of my material has convinced me 

 that I was mistaken, and that in the anaphase there are 16 very small 

 chromosomes at each end. The process actually takes place as follows. 

 When the spindle is formed, 16 chromosomes arrange themselves in 

 the equatorial plate in such a way that they are generally closely as- 

 sociated together in pairs, sometimes more closely paired than in the 

 Fig. 1 of my former note. But it may sometimes be seen that each 

 individual member of the pair is in itself double or dumb-bell-shaped, 

 and when the division takes place the members of a pair are not se- 

 parated from one another, but each divides so that the 16 halves pass 

 to each pole. The 8 chromosomes shown in my Figs. 2 and 3 there- 

 fore represent 8 pairs of chromosomes in close approximation, each 

 single one of which divides as shown. My results are thus in essential 

 agreement with the statements of Mark and Copeland (Proc. Amer. 

 Acad. Arts and Sei., Vol. 42, No. 5, p. 103). 



The arrangement of the chromosomes in pairs in the equatorial 

 plate of the final maturation spindle, which led to my misinterpretation, 

 has a further interest, for it may throw light on the statements of 



