BLACKMAN: THE SPERMATOGENESIS OF SCOLOPENDRA. 25 



i. Maturation Divisions in the Large Spermatocytes. 



A. Division of the First Spermatocytes. 



In the prophase of the spermatocytes of the large type, the first 

 changes observable have to do with the centrosomes and archoplasm. 

 The two centrosomes, which up to this time have apparently lain passive 

 in the cytoplasm surrounded by their special envelope of archoplasm, 

 now show signs of activity. The two parts, heretofore quite distinct, 

 come together and partly coalesce to form a dumbbell figure which, 

 surrounded by a small sphere of archoplasm, then begins to migrate 

 toward the nucleus. During this migration the idiozome gradually 

 diminishes in size, and synchronously very faint astral rays begin to 

 appear. Finally by the time the centrosomes reach the nuclear 

 membrane the granular structure of the centrosphere has disappeared, 

 and this body is now represented by a small colorless, structureless mass 

 surrounding the centrosomes, through which the feebly developed astral 

 rays extend (Fig. 20). The centrosphere at this time fails to take the 

 stain, and is apparently composed of the same substance as that occupy- 

 ing the interstices of the cytoplasmic reticulum. 



While these changes are occurring, the archoplasm surrounding the 

 entire nucleus disintegrates and upon superficial examination seems to 

 have entirely disappeared. The cytoplasm has also altered considerably 

 in appearance. Its reticular structure is no longer as apparent as 

 formerly, and it retains the stain more strongly and appears considerably 

 more dense. The archoplasm as it disintegrates is converted into a 

 liquid or semi-liquid very finely granular mass, which is disposed evenly 

 throughout the cell in the meshes of the cytoplasm. Here, mixing with 

 the fluid hyaloplasm, it causes this inter-reticular substance to stain 

 much more deeply, and thus alters considerably the general appearance 

 of the cytosome. 



As the compound centrosome approaches the nucleus, the nuclear 

 membrane is often drawn out into a cone-shaped protuberance, as shown 

 in Figure 20. This is probably caused by an attractive force exerted by 

 the centrosome. Soon after reaching the membrane the centrosome 

 again divides into its two parts, which separate and begin their slow 

 migration toward opposite poles of the nucleus. 



In his work upon the spermatocytes of Scolopendra dalmatica Carnoy 

 I 85), however, states that the centrosomes do not migrate apart upon 

 the nuclear membrane, but that they move through the cytoplasm at a 



