440 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Echiuroid Thalassema mellita Conn, and of the " boring clam," Zirphsea 

 crispata. In both cases the astral systems agree closely with Boveri's 

 descriptions for Ascaris. There is a central focal granule (centriole) 

 surrounded by a cloudy area (the centrosome), which is again enclosed 

 by the ckar centrosphere with its dense crown of astral rays. But of 

 these parts it is the focal granule which alone meets Boveri's definition 

 of the centrosome — " the single permanent cell-organ which forms the 

 dynamic centre of the cell, and multiplies by division to form the centres 

 of the daughter-cells " ; it is the focal granule alone which persists 

 throughout all stages, divides, and apparently initiates mitotic activity. 

 Rays, centrosphere, and cloudy area, are formed only during prophases 

 and metaphases ; when the anaphase begins they break down and dis- 

 appear, while the centrosome migrates to the periphery of the sphere, 

 and sets up a new system. 



In both Thalassema and Zirphsea a reducing division occurs. In the 

 former case the first polar division is a longitudinal (equation) division, 

 the second a transverse (reducing) division. In the latter the same 

 process seems to occur, but it is not possible to say which division is the 

 reducing division. In the occurrence of a reducing division the two 

 forms resemble Insects and Copepods. 



Mitotic Figures in Ovarian Ova of Mammals.* — Herr J. Sobotta 

 comments upon an observation of A. Spuler's j that he saw a spindle 

 figure in an ovum in the ovary of a pregnant guinea-pig — an observation 

 from which he drew the conclusion that ovarian ova in mammals may 

 divide by mitosis. Sobotta has also seen central spindles in the ovarian 

 ova of the mouse, but he is convinced that these represent the first 

 directive spindles. In the mouse, according to Sobotta, the first polar 

 division is usually suppressed and only one polar body liberated. 



Structure of Ovary of Rabbit4 — M. Charles Honore has investi- 

 gated those structures in the follicular epithelium of the rabbit, which 

 were first described by Call and Exner, and later named " epithelial 

 vacuoles " by Flemming. The author finds that they have an intercellular 

 origin, and are to be regarded as a special product of the activity of 

 certain cells of the granular membrane of the Graafian follicle. They 

 are primitively compact and homogeneous, but become vacuolised by 

 imbibition of liquid. This vacuolisation occurs at the time when the 

 follicular liquid is secreted by the granular layer, and the bodies appear 

 to exercise an influence on the rupture of the cellular partitions which 

 extend from the discus proligerus to the parietal granulosa. The bodies 

 pass out of the follicle at its dehiscence, and take no part in the forma- 

 tion of the corpora lutea. 



In a further communication the author discusses the formation of the 

 corpora lutea. He finds that the follicular epithelium persists intact 

 until the rupture of the follicle, and shows no trace of degeneration. 

 The yellow cells of the corpora lutea are the epithelial cells of the 

 follicle which have become hypertrophied. This hypertrophy, together 

 with the interpenetration of connective-tissue, accounts for the increase 

 in volume of the corpus luteuni as compared with a fre>hly ruptured 



* Festschr. Phys. Med. Ges. Wiirzburg, 1899, pp. 186-292 (1 pi.) See Zool. 

 Centralbl., vii. (1900) p. 380. f Verhandl. Anat. Ges., 1899, p. 22. 



J Arch. Biol., xvi. (1900) pp. 537-99 (3 pis.). 



