232 First Maturation Spindle of Allolobopliora Foetida 



interpretation for the first division, in Thalai^sema the first division 

 being longitudinal (giving to each cell one-half of every univalent 

 chromosome) , and in Allolobopliora transverse (giving to each cell entire 

 univalent chromosomes, each receiving one-half the somatic number). 

 Griffin has clearly stated his results in the following summary : 



"1. By longitudinal fission and transverse segmentation of the 

 spireme thread, there arise 12 (reduced number) ellipse-shaped chromatin 

 masses. 



" 2. These persist throughout the growth period of the egg. 



" 3. During prophase they concentrate into crosses, the arms of which 

 are tight loops. 



" 4. In the first polar division these are drawn out again into ellipses 

 which divide to form daughter- Y^s (equation division). 



" 5. The V's break apart at the angle in the second polar division (re- 

 ducing division)/^ p. 612. 



The persistence of the chromosomes throughout the entire growth 

 period, during the time that the nuclear reticulum is gradually develop- 

 ing, led Griffin to the conclusion that " its development is independent of 

 the chromosomes which are passive during its growth" (p. 604), and 

 Griffin's conclusions as to the independence of these two substances are 

 supported by our observations on Allolohophora. The two Annelids are 

 further in accord as to the first appearance of the maturation centrioles. 

 In both types they are first seen as minute asters close to the germinal 

 vesicle, though in Thalassema they are closer to each other than we have 

 yet found them in Allolobopliora. This independence of the centrioles 

 accords with Mead's observation on Chcetopterus, '98 (cf. our Photos. 

 81 and 82, Plate V, with Mead's Figs. 8 and 9). The two extremely 

 small centrioles of the above-mentioned photographs show a more marked 

 independence of origin than those figured by Mead, for they are at oppo- 

 site poles of the germinal vesicle, while closer to its membrane and at an 

 earlier stage of development than those figured for Chcetopterus. These 

 primary asters of Chcetopterus " arise at some distance from the wall 

 of the germinal vesicle," and Mead adds : " I am not prepared to say at 

 present v/hether the primary asters are formed by the further growth 

 and specialization of two of the secondary asters or by the union and 

 coalescence of several." These secondary multiple asters which Mead 

 has demonstrated in his Fig. 7, he has shown to be normal in Chatop- 

 terus, having watched the phenomena in living eggs, which continued to 

 develop after the multiple asters had disappeared. In Allolobopliora we 

 have found only one egg showing structures that could be interpreted as 

 multiple asters, but the egg was unquestionably pathological, the germinal 



