The Mickoscope. 123 



vigorous, until at last the embryo bursts through, and, propelled by 

 a wreath of delicate frontal vibratile cilia, it soon finds its way out 

 of its mother's domicile, and swims rapidly I'ound its parent; then 

 strikes out with a graceful motion through the water, poking among 

 the weeds in quest of a fitting place to start house-keeping on its 

 own account. 



Human Ovum. — Dr. W. Nagel communicates a description of the 

 human ovum, in I'egard to which there has been a lack of precise 

 information. His material was obtained from ovaries removed in 

 operations. Healthy follicles were isolated and examined, and in 

 other cases sectioned m situ. 



The zona pellucida is very distinct, and is separated by an 

 extremely fine "• perivitelline space " (apparently containing clear 

 fluid) from the vitellus. Within this is the narrow, clear " cortical 

 layer" of vitellus, then a somewhat broader, finely granular "proto- 

 plasmic zone," then the " dentoplasmic portion," with abundant 

 globules, more abundant and less refractive than in the ova of the 

 domestic mammals. 



The nucleus is round, clear, double -contoured, always eccentric, 

 and in the protoplasmic zone. There is a distinct nuclear network. 

 The nucleus exhibits amoeboid movements. 



The corona (epithelium of ovum) was always well developed on 

 ripe eggs. The diameter of the ripe ova varied from 124-128 mm. The 

 various zones vary somewhat in different regions. The nucleus 

 measured 19-20 mm. 



In the ovaries of new-born subjects, besides the usual primordial 

 follicles, larger follicles were observed (Waldeyer-Slavjaushy). In 

 these, sections revealed normal ova, and the author does not, therefore, 

 regard the presence of these large follicles as indicative of incipient 

 cyst- formation. 



In development, the protoplasm and nucleus increase in size, 

 the follicular cells multiply, the dentoplasm is formed, the nucleus 

 is pushed to the side, and a zona pellucida begins to appear. — Roy. 

 Mic. Journal. 



NEWS AND NOTES. 



The proper committee in Congress has recommended the 

 removal of duty on alcohol which is to be used in the arts and 

 manufactures. 



Mr. Douglas H. Campbell, of Detroit, has an interesting sketch 



