A Cytological btiuh- of the Senii-pararitic Copepod, Hersilia apodiformis etc. 419 



logical difference between tliese two chromosomes. The stout fibers 

 passing from them to the sister groups of chromosomes are very notice- 

 able; the position of the hetero-chromosomes in relation to the spindle 

 is very variable — at times one or both lying with their longitudinal 

 axis transverse in the spindle, and again parallel to the spindle, showing 

 indications of a "Querkerbe". Figm'e 32 points out that the "hetero- 

 chromosomes" do not divide in the first maturation mitosis, but that 

 they separate reductionally like the autosomes, one passing wholly to 

 each second spermatocyte. [In the cytoplasm of Figure 32 (also Figs. 28, 

 29) is Seen a dark body, which is probably a portion of the "nuclear cap".] 

 In this stage the fibers from the hetero-chromosomes to the opposite 

 group of chromosomes is still visible. 



The division of the cell body of the primary spermatocyte into second- 

 ary spermatocytes is not necessarily concomitant with the Separation 

 of the chromosomes into two groups. In fact, the division of the cyto- 

 plasm may not occur at all — two interkinetic spermatocytes or two 

 second spermatocyte spindles (Figs. 37, 39) being found often in one 

 cytoplasmic mass. The other extreme is shown in Figure 38. Here 

 the cell body has evidently divided while one of the lagging hetero-chromo- 

 somes was stiU in the equator. The hetero-chromosome is seemingly 

 held fast by the newly formed membrane between the sister spermato- 

 cytes, and is attached to both of the sister groups of chromosomes, which 

 have arranged themselves for the second spermatocyte division. Two 

 clear cases, such as illustrated in Figure 38, came under my Observation; 

 and, I believe, that it is not unlikely that such irregularities in the dis- 

 tri])ution of the chromatin, as this would })ring about, may be associated 

 with the occasional appearance of a hermaphroditic individual. A further 

 consideration of this point and a description of a hermaphroditic sex gland 

 (Fig. 4, Plate IVj will be found on pages 435—436. 



In the interkinetic period (Figs. 33 a—h), the chromosomes do not 

 enter into a net-work but remain plainly visible. The forms assumed 

 by the chromosomes, are of interest; for on similar figures in the oögenesis 

 of Cyclops hrevicornis, Haecker ('02; '04; '07; '10) founded his theory 

 of "Interkinetic Symmixis through Permaitation". 



BRA.UN ('09) and Matscheck ('10), from their observations on Cy- 

 clops viridis, have ah'eady raised objections to the facts upon which this 

 theory Stands. Hersilia presents still further objections. Although the 

 longitudinally split chromosomes of the interkinetic nuclei usually remain 

 in contact only at the "Querkerbe", this does not always produce sym- 

 metrical X-figures, for the "Querkerbe" may be nearer one end than 



