BIGELOW : NUCLEAR CYCLE OF GONIOXEMUS MURBACHII. 313 



the same finely reticulate appearance as in the earlier generation. I 

 have been unable to detect any archoplasmic structures whatever, nor is 

 the presence of a centrosome to be demonstrated with certainty, although 

 minute granules are often found which might be supposed to represent 

 that structure. The cytoplasm does occasionally, however, contain small 

 metaplasmic masses similar to those described in the last cell generation 

 (see page 304, and compare with Figs. 15 and 17), though they are here 

 much smaller (Fig. 40), and often not to be found at all. "When pres- 

 ent, they ai'e closely apposed to the nuclear membrane, and disappear 

 during the prophase. The staining reactions of the cell closely parallel 

 those of the spermatogonia. With the Auerbach mixture, the best micro- 

 chemical test easily available for fixed material, the nuclear membrane, 

 reticulum, and karyosomes select the red (acid) dye, while the nucleolus 

 stains a very pure green, which of course indicates that it is very rich 

 in nucleinic acid. 



3. The First Maturation Division. 



Prophase. — The early prophase of the first maturation division closely 

 resembles that of the somatic and spermatogonial mitoses. The karyo- 

 somes increase in size, and become denser and more sharply outlined, 

 and it is evident that hand in hand with their increase in bulk the 

 nucleolus suffers a corresponding decrease in volume until it finally dis- 

 appears entirely (Figs. 42 and 43, which represent two successive stages 

 in this process). The prophase, then, is in so far a reversal of the telo- 

 phase of the last spermatogonial division, as the nucleolus, then formed 

 through the coalescence of numerous chromatin masses, now disinte- 

 grates through their dispersal. Guenther (:04) was able to find in 

 the spermatocytes of Hydra all stages from such a nucleolus to the 

 definitive chromosomes ; but he gives no figures of the process, nor does 

 he describe it in detail. Downing (:05), on the other hand, makes no 

 mention of any nucleolus in primary spermatocytes of Hydra. 



Shortly before the disappearance of the nucleolus, the karyosomes 

 reverse their staining reaction, now exhibiting the characteristic affinity 

 of chromatin for basic dyes — a change which is nearly simultaneous 

 with the disappearance of the karyoplasm. The nucleus is now (Fig. 

 44) filled with a complicated i-eticulum, which bears at its nodes and 

 along the course of its meshes a great number of small chromatin 

 masses, the karyosomes. I have not been able to count these accurately, 

 nor do I believe that their number is important. On the contrary, I 

 regard it as probable, from their variations in size, that they also vary in 



