STUDIES ON INSECT SPERMATOGENESIS. 69 



philic core. The first of these expectations receives a remarkable 

 fulfillment in many insect forms, and I am not aware that the se- 

 quence is ever certainly violated. The Lepidoptera, as described 

 by Meves ('oo) and Gatenby ('17) are particularly good ex- 

 amples, and many Coleoptera exhibit a similar condition. Thus, 

 in Slip ha, Holmgren ('02) figures very clearly the gradual disap- 

 pearance of the chromophilic material as the undivided nebenkern 

 draws out, and, in cross-sections very similar to those which I have 

 figured, he shows that the division furrow of the nebenkern ex- 

 tends only to the periphery of the chromophilic core (his " Mito- 

 chondrienrestkoerper "). Shaffer Ci/) figures a similar stage in 

 Passalus, which he seems to think is divided. From the position 

 of the nebenkern parts, I think, however, that the conditions are 

 like those in Silpha, Shaffer having confused the indications of 

 division with the accomplished fact. Still other cases might be 

 cited, all of which tend to support my contention that the division 

 of the nebenkern is never completed until the chromophilic sub- 

 stance has disappeared. It remains, then, to inquire whether, in 

 these cases of delayed division, the disappearance of the chromo- 

 philic material is followed by the definite splitting of the neben- 

 kern. The evidence on this point is very scanty since, if division 

 is long delayed, it would usually be overlooked. However, in 

 the case of Silpha (Holmgren ('02)) the whole history of events 

 is clear, and Holmgren's figures show conclusively that the neben- 

 kern completes its division after the disappearance of the chro- 

 mophilic substance. In the case of Passalus, if my interpretation 

 of Shaffer's Fig. 21 be correct, the nebenkern is subsequently 

 divided, as shown by his Fig. 2oc, though the exact relation to the 

 disappearance of the chromophilic material is not established. 

 The classical case of the lepidopteran nebenkern has never been 

 followed out in detail, and it would seem that the chromophilic 

 material retains its identity for a long period. But I will venture 

 the guess that in this case, also, a division of the nebenkern will 

 be found to occur once the chromophilic substance has been dis- 

 posed of. 



This completes the history of the origin and nature of the 

 " blackberry " and " onion " patterns which were mentioned in the 



