ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 393 



penetrate to the yolk and load themselves with yolk-granules and pig- 

 ment. Then begins a mesodermic immigration of cells and blood- 

 vessels, which carry out the absorption, as in the formation of the 

 normal corpus luteum. The egg becomes smaller, more densely and 

 uniformly black, and disappears. During the degeneration of the ripe 

 eggs, the growth and new formation of fresh eggs may be seen continuing 

 without any hindrance if the nutritive conditions are good. 



b. Histolog'y. 



Structure of the Cell.*— A. Perroncito has studied this in the 

 spermatogenesis of Paludina vivipara. He deals with the various com- 

 plications which have been recognized within the cell of recent years 

 — the accessory nuclei, Golgi's internal reticulum, the motochondria of 

 Benda, the trophospongia of Holmgren, the pseudo-chromosomes, central 

 capsules, centrof ormia, and chromidia. 



He finds that Golgi's internal reticulum and the mitochondria are 

 distinct, and may be seen at the same time in one cell. Moreover, there 

 are two kinds of mitochondria — the mitochondria of Benda and the 

 chromosomes of Meves. Golgi's reticulum is an essential part of the 

 cell and has an important role. It shares in a definite way in cell- 

 division, passing through typical stages and breaking up finally into 

 the two reticula of the daughter-cells. This intricate process is called 

 diktokinesis. Its first phases are completed while the nucleus is still at 

 rest. 



The mitochondria do not quite correspond to Altmann's " bioblasts " 

 or to Flemming's " filar mass." Suppositions as to their role as vehicles 

 of inheritance are still lacking in corroboration. There is great uni- 

 formity in the structure of the developing and complete spermatozoa in 

 diverse types. 



Ceil-structure.f — Hch. Stauffacher discusses in the first place the 

 nuclear membrane, in which he does not believe. The oxychromatin of 

 the nucleus passes directly into that of the cytoplasm, and there is neither 

 an achromatin nor a chromatin membrane. In the case of the macro- 

 nucleus of Ciliata, there are clear bridges binding the oxychromatin to 

 that of the micronucleus and to that of the surrounding cytoplasm. The 

 macronucleus is very rich in basichromatin, the micronucleus has a 

 relatively small amount. 



A study of the ova in Anodonta shows more or less nuclein in the 

 nucleus of young ova, but none in the nucleus of ripe ova. Nuclein has 

 to do with growth and metabolism. The head of the spermatozoon is 

 full of nuclein, and it may l)e that this acts as a ferment on the ripe 

 egg, setting processes of growth agoing. In the germ-cells of a Trema- 

 tode sporocyst, which develop parthenogenetically, there is abundant 

 nuclein. 



Structure of Erythrocytes and Blood- plates.^ — V. Schi 11 ing-T organ 

 derives the erythrocytes from leucocytes, with ectoplasm and endoplasm, 



* Arch. Mikr. Anat., Ixxvii. (1911) Heft 3, Abt. i., pp. 311-21 (6 figs.). 



t Zeitscbr. wiss. Zool., xcviii. (1911) pp. 478-527 (Ipl. and 5 figs.). 



X Verb. Anat. Ges., 1911. Anat. Anzeig., xxxviii. (1911) pp. 188-94 (19 figs.). 



Aug. 21d, 1912 2 e 



