CYTOLOGY OF ANISOLABIS MARITIMA BON. 239 



ures 1-4 (Plate XXIV) represent four typical metaphase plates. 

 Subsequent observations lead the author to believe that, of the 

 twenty-six chromosomes, twenty-two are autosomes, and four 

 are two double x-chromosomes, which appear in quiescent 

 oogonial nuclei as two double and almost square karyosomes. 

 The female somatic number has likewise been established' 

 to be 26. The counts were made on well-developed embryos, 

 treated by the same methods as the gonads. Numerous mitoses 

 in the hypodermal cells and in the developing central nervous 

 system offered abundant material for statisfactory counts. A 

 suitable embryo would be selected and then sketches made of 

 every distinct metaphase plate. in the whole series of sections. 

 Figures 5-8 (Plate XXIV) represent four groups showing 26 

 chromosomes each. These are selected from a single embryo in 

 which dozens of clear counts of 26 were made. In the somatic 

 cells, as has been noted by previous investigators, there is a 

 much greater variation in the size of the cells and the form of the 

 chromosomes (whether long and narrow, or short and broad) than 

 there is in the germ cells. The chromosome number, however, 

 remains constant, with the occasional exception of a giant cell 

 with twice the diploid number present. 



B. The male 



Spermatogonia likewise have clear, clean-cut chromosomes, 

 twenty-five in number, cells near the apex of the tubule serving 

 best for such counts. These spermatogonia have a large amount 

 of cytoplasm and the chromosomes are well separated (Plate 

 XXIV, figs. 9-12). In the cytoplasm onemay often encounter 

 bodies, which might be mistaken for chromosomes in deeply 

 stained haematoxylin preparations, especially after Bouin or sub- 

 limate fixation. In such preparations these cytoplasmic masses 

 are quite as dark in color as the chromosomes and not greatly dif- 

 ferent in size from the average Anisolabis chromosome. These 

 bodies are shown, light gray in tone, in figures 9, 11, and 12 of 

 Plate XXIV. After Benda fixation these cytoplasmic bodies take 

 mitochondrial stains, and stand out in marked contrast to the 



