A Cytological Study of the Semi-parasitic Copepod, Hersilia apodiformis etc. 407 



ventral tube itself. Fiat nietaphase plates are far from nunierous but 

 propliases and anaphases can be observed in almost every testis. 



In the quiescent spermatogoniiim (Plate V, Fig. 5), there is a fine 

 network over whicli the chromatin is scattered, not evenly, but massed 

 more or less into clumps. Within the nucleus, as a rule, are two spherical 

 nucleoli, usually of unequal size; but at times a single nucleolus, larger 

 than these paired nucleoli, occurs in the spermatogoniuni. Haecker 

 ('02) figured such paired nucleoli for Heterocope (his Fig. 23, Taf. II), 

 using them as evidence for the parental duality of the spermatogonia. 



Lying on the nuclear membrane in the cytoplasm are scattered, in 

 varying number and size, disks of a substance which stains like the nu- 

 cleoli. Thus in a double stain, Delafield's haematoxylin and Orange G, 

 they take on a deep orange color. In carmine, after Carnoy fixation, 

 they remain light pink, whereas the chromatin is deep red. Heidenhain' s 

 haematoxylin, gentian-violet, crystal-violet and safranin stain the disks, 

 the nucleoli, and also the chromosomes. The staining reaction in Dela- 

 field's haematoxylin and carmine would indicate that these disk-like 

 bodies are not chromatic, but more of the nature of true nucleoli or plasmo- 

 somes. In as much as they occur in the cytoplasm we may call them 

 "cyto-plasmosomes". These "cyto-plasmosomes" are very much in 

 evidence during the growth period of the spermatocytes; and it is well 

 to note that they are already present in the spermatogonia, and are not 

 extruded from the spermatocyte nuclei in the period of greatest meta- 

 bolic activity. 



In preparing for mitosis the fine network becomes less evident and 

 the chromatin fornis long angular bands (Plate V, Fig. 6), which are 

 not joined together in a spireme. The nucleoli are still plainly visibles 

 at this stage. The chromosomes then shorten, take on a more honio- 

 geneous character, and stain more deeply (Plate V, Fig. 7). At the 

 middle or near the middle they show a marked tendency to form an angle. 

 These angles are probably an indication of the "Querkerbe", which first 

 comes into piain view in the contracted chromosomes of the metaphase 

 plates. And now the nucleoli can no longer be recognized. Figure 8 

 represents a metaphase (equatorial) plate, in which twenty-four chromo- 

 somes are present, many of them showing a light transverse streak 

 or "Querkerbe". The "Querkerbe" usually marks the chromosome into 

 two equal parts, but not without exceptions. At least two pairs are 

 asymmetrically segmented — a fact supported by the chromosomes in 

 the metaphase plates of the second spermatocyte (Plate VI, Fig. 35) 

 and the primary oöcyte (Plate VI, Fig. 49). Two short chromo- 



