BAUMGARTNER : SPERMATID TRANSFORMATIONS. 55 



foremost when set free into the vas deferens. Fig. 42 may in- 

 dicate some such behavior. 



(c) THE SPERMATOZOON. 



The mature spermatozoon consists : (1) of a sharp, spear-like 

 point; (2) a tube-like head about .02 mm. long, composed of a 

 densely staining outer wall and a clearer central cavity ; and 

 (3) a filamentous tail about .5 mm. long. The point comes 

 from the acrosome, the head from the nucleus, and the tail 

 from the axial filament and nebenkern. While I do not deny 

 the presence of a middle piece, my observations do not warrant 

 me in describing one, although fig. 40 would suggest it. 



IV. Comparison of Results. 



Dr. R. von Erlanger ('97, 1, and '97, 2) and Dr. F. Meves ('00) 

 have given excellent discussions of the literature on the neben- 

 kern. I cannot do better than direct the attention of other in- 

 vestigators to them. Hence, I shall discuss only such authors 

 and such points as have special bearing on my own results. 

 The spermatid changes in the Gryllidse have been studied, so far 

 as I know, only by St. George ('67) and by vom Rath ('92). 



St. George, in his early paper, described the transformation process in the 

 "Hausgrille" along with other insects. He found the "Nebenkorper," and saw 

 that it took a part in forming the envelope of the axial filament, a small particle 

 remaining near the nucleus and other drops of it appearing at intervals on the 

 tail. In his paper on Blatta ('86, 1) he accepted Biitchli's name, "nebenkern," 

 and traced its origin to the spindle remains. In his paper on Phratora ('86, 2) 

 he takes up the description of the nebenkern in the spermatocytes and spermato- 

 gonia. In the spermatid, he describes the blackberry stage in these words : 

 " Wahrend das andere (not nucleus) Korperchen weniger lebhaft gefiirbt als ein 

 kleiner Fadenknauel mit unregelmassigem Contour erscheint." 



There can be no true nebenkern in the spermatogonia and 

 spermatocytes, as St. George first used the word, and as I have 

 limited its application. But St. George found the object, traced 

 its origin and fate, and described several of the stages as they 

 appear in Gryllus. 



Vom Rath ('92) found Qryllotalpa very poor material for following the 

 spermatid changes. However, he described an oval body which he found varied 

 in appearance, depending on the method of fixation. He calls it the " nebenkern" 

 and thinks it goes to help form the tail. 



The description is too incomplete for comparison. Judging 

 from Gryllus, I question its being very poor material. 



Butschli ('71) studied the spermatid transformations in Acrididre and Locus- 



