422 Sidney I. Koriüiauser 



the constancy of the normal niimber of chromosomes in the development 

 of the individual; and with the observations of Agar ('12), as to the 

 presence of a "Querkerbe" in the mitoses of the embryo. 



B. Primordial Germ Cells. 



In the Wastulae (Fig. 53) and gastrulae the two large primordial 

 gerni cells (ug.) remain quiescent; but the chromosomes. instead of enter- 

 ing into a network, remain compact, — in fact, they stain as deeply 

 and clearly as chromosomes in mitosis. Counts of such cells (Fig. 54) were 

 not difficult and gave the normal number, twenty-four. The chromo- 

 somes are longitudinally split and show also a "Querkerbe", so that they 

 often appear as tetrads. Amma ('11) found in the primordial germ cells 

 of Cyclops fuscus (var. distincius) eleven chromosomes, and in Cyclops 

 strenuus, twenty-two chromosomes, all longitudinally divided and show- 

 ing a "Querkerbe". He stated that Schiller's figures of tetrads, pre- 

 sumably brought forth by cutting the egg sacks (Schiller '10, Fig. 40, 

 p. 591), were similar to those found in normal material. Hersüm certainly 

 Supports Amma's contention, for a longitudinally spht chromosome with 

 "Querkerbe" appears in the form of a tetrad, and, ^\]len division is de- 

 layed, as in the interkinetic phase of Hersilia (Figs. 33 and 34), the halves 

 of the chromosomes remain in contact at the "Querkerbe" and open 

 out to form X-figures. In experiments dealing with the effect of ether 

 and Chloroform on the cleavage chromosomes, Schiller represents X- 

 forms very frequently and describes them as tetrads. It is not improb- 

 able that these are merely normal, longitudinally split chromosomes, 

 delayed in mitosis through the effects of the narcotics upon the spindles, 

 and are not comparable to the tetrads of the fü*st maturation division. 



IX. Discussion. 



A. Form and Number of the Unredueed Chromosomes. 



The results on Hersilia go to show that the diploid number of chromo- 

 somes appears in the spermatogonial and oögonial mitoses and the haploid 

 number in the meiotic spindles. This fact, while agreeing with the mat- 

 uration phenomena in general in both animal and plant kingdoms, comes 

 into conflict with a great many of the previous works on the Copepods. 

 These works may be classified under two categories: 1) those maintain- 

 ing that the reduced number of chromosomes are present in either the 

 oögonial or the primordial germ cells (Haecker '95 b; vom Rath '95; 



