PROPHASES AND METAPHASE OF THE FIRST MATURA- 

 TION SPINDLE OF ALLOLOBOPHORA FCETIDA. 



BY 



KATHARINE FOOT AND E. C. STROBELL, Woods Holl, Mass. 

 With 9 Plates. 



In the most mature eggs found in the ovaries of AUolohopJiora 

 fa'tida, the germinal vesicle is intact, the large nucleolus is present and 

 the chromosomes are not 3'et formed. 



In the eggs of the freshly deposited cocoon, the first maturation spin- 

 dle is at the metaphase.' From the time, therefore, that the eggs leave 

 the ovaries, until they reach the cocoon, the prophases of the first matura- 

 tion spindle take place, i. e., the forming of the chromosomes, the 

 breaking down of the germinal vesicle, and the disappearance of the 

 large nucleolus. In the summer of 1901, we found that these stages of 

 development occur, while the eggs are in the reccptacula ovorum ' 

 and we have thus far ol)served no exception to this rule. 



In an earlier paper (Foot and Strobell. '02), we demonstrated that these 

 worms deposit their cocoons about every third day, and it is therefore 

 probable that the eggs accumulate in the receptacula during this 

 period, indicating that the development of the eggs })i-ogresses very slowly 

 in the rcceptacuUnn ovorum. The earliest stages shown by these eggs, 

 have the germinal vesicle intact, with the nucleoplasm still undiffer- 

 entiated into distinct chromatic and achronuitic substances, a large 

 nucleolus with one or more vacuoles, and no indication of any centriole 

 or rays in the cytoplasm, while the most mature eggs have the first 

 maturation spindle at the metaphase. 



' We have found only one egg in which the chromosomes are not oriented 

 in the equator of the spindle. The normal stage of development appears to 

 be the metaphase of the first spindle, though there are many degenerated 

 and disintegrated eggs, some showing a vestige of a germinal vesicle but 

 with no differentiation of the nucleoplasm, the chromatin being disintegrated 

 and structureless, and in only one or two cases have we found even an indica- 

 tion of a persisting nucleolus. 



^Marshall and Hurst state in their text book, "Practical Zoology" (1888), 

 that immature eggs may be found in the receptacula ovorum of Lumbricus 

 at certain seasons of the year. 

 American .Journal of Anatomy. — Vol. IV. 



