6 1 6 GRIFFIN. [Vol. XV. 



metakinesis and various stages in the division. Garnault ('88) studied both 

 Arion and Helix and describes the first polar body as dividing mitotically 

 with or without the formation of a resting-nucleus. In numerous insects 

 (Blochmann, '87, '89, and Hertwig, '90) each of the two groups of daughter- 

 chromosomes of the first maturation-spindle divide at telophase while still 

 within the egg, giving rise to four groups of chromosomes. These pass into 

 four resting-nuclei (the female pronucleus and three polar nuclei). Vejdovsky 

 ('88) has described the mitosis of the first polar body in Lumbricus rubellus 

 lirvA. Allolobophora foetida. A completed spindle is figured of the latter, with 

 one well-developed aster. The spindle lies in the greatest diameter of the 

 polar body, which is here radial and not paratangential. 



A mitotic division, or at least some of the initial stages, has been also 

 noted in numerous insects (Blochmann, '87), in Amphibians (Schultze, '87), 

 Myzostomutn (Wheeler, '95), the Mouse (Sobotta, '95), Phallusia (Hill, 

 '95), and other forms. Quite recently Korschelt ('95) has described, in 

 some detail, the nuclear changes in the polar bodies of Ophryotrocha, in 

 which considerable variation appears to exist. 



From the above it appears that the phenomenon in question is a pretty 

 general one ; that in some cases it results in a complete division typically 

 mitotic ; but that more often the attempt is abortive and the process ceases 

 with the attainment of some intermediate stage. In a few cases a resting- 

 nucleus may intervene previous to the division. 



PART II. — ZIRPHAEA. 



V. Development of Ova. 



The earliest ova that can be easily recognized as such have 

 more or less oval nuclei, measuring about 6 by Q/it in diameter. 

 They lie imbedded in the stroma of the ovarian tubules, 

 with a minute quantity of cytoplasm heaped on either side. 

 A cell membrane could not be demonstrated with certainty. 

 The large, dark-staining nucleolus is single and eccentric. 

 The nuclear reticulum is as yet represented by a few strands 

 only. Peripherally situated chromosomes are occasionally to 

 be observed. The ovum has clearly passed out of the spireme 

 stage and has entered the growth period. During the growth 

 period numerous nuclei that stain a brilliant green with Auer- 

 bach's fluid are present in considerable number, some scattered 

 irregularly throughout the stroma, others closely appressed 

 against the growing egg. They are evidently nutritive nuclei. 



In the earliest stages the cytoplasm of the growing egg takes, 



