498 PROCEEDINGS OF THE AMERICAN ACADEMY. 



first spermatocyte mitosis, although in later stages they are reduced 

 to smaller granules. In Scutigera (Modes, :05) structures which are 

 probably homologous are formed both in the nucleus and in the cyto- 

 plasm. These bodies, which are classed as metaplasm, stain densely 

 and vary widely in number in different cells. As the prophase ap- 

 proaches, they begin to disintegrate, and soon disappear entirely. 



In Scolopendra (Blackman, :05) there are two sorts of formations 

 occurring in the cytoplasm. The first of these is the archoplasm, 

 which is similar in structure to the cytoplasm and appears as a thick- 

 ened and condensed part of it. The second consists of rather small, 

 dark staining granules, which in appearance and behavior are similar 

 to those in Scutigera. These undoubtedly represent metaplasm — 

 either ingested food particles, or by-products of the cell activity. 



In well-preserved cells of the three species of Lithobius studied 

 I have been able to find no structures corresponding to the " forma- 

 tions ergastroplasmiques " of P. et M. Bouin, although in sections of 

 poorly fixed material such deposits are often seen. The cytoplasm in 

 Lithobius is very fine meshed and seems to be very difficult to fix 

 properly. When wrongly treated, the fine reticulum becomes dis- 

 torted and irregularly massed together in such a manner as to give 

 the appearance of definite structures, and these I believe have been 

 incorrectly regarded as normal structures. However, a few small, dis- 

 tinct granules do seem to be present at all stages of the first sper- 

 matocyte, and these I consider to be metaplasm, i. e., food material or 

 by-products of metabolism. 



In Lithobius no such aggregations of archoplasm exist as are char- 

 acteristic of the growth period and vesicle stage of Scolopendra. On 

 the contrary, all of the cytoplasm of the cell seems to be of about the 

 same consistency. Indeed, both in structure and staining reactions 

 the cytoplasm in the vesicle stage is quite similar to that in the pro- 

 phase of the first spermatocyte of Scolopendra, after the archoplasm 

 has been dissolved in the hyaloplasm and dispersed throughout the 

 entire cell. This similarity and the fact that there are no special 

 aggregations of archoplasm have led me to conclude that during the 

 vesicle stage in Lithobius the archoplasm is dispersed throughout the 

 cell. This causes the cytoplasm at this stage and during the early 

 phases of mitosis to stain more strongly than at other times. 



At the completion of the growth period the spermatocyte of Litho- 

 bius mordax in the vesicle stage presents the appearance shown in 

 Figure 10. The size of the cells is remarkable, as they often reach an 

 average diameter of more than 100 micra, thus being even larger than 

 the spermatocytes of Scolopendra and Scutigera. In the various 



