February 3, 1899.] 



SCIENCE. 



.169 



remain in the water until the formation of 

 the first polar spindle, before being fertilized. 

 The second cleavage takes place about 24 

 minutes later ; the third cleavage occurs af- 

 ter SO minutesmore; the fourth after another 

 o5 or 40 minutes; and after a further lapse of 

 about 50 minutes, or in a little less than 3i 

 hours after fertilization, the fifth division, 

 with its resulting 32 cells, is completed. A 

 very symmetrical blastula appears about 7^ 

 hours after the eggs are fertilized, and in 

 \}j; hours more the embryos begin to swim. 

 The third cleavage, which is distinctly right- 

 handed, shows the first differentiation of 

 the cells in regard to size ; the upper four, or 

 those next to the polar bodies, being slightly, 

 though perceptibly, larger than the lower 

 four. The cleavage is typically spiral and 

 almost perfectly regular. There are only 

 the slightest indications of a vitelline mem- 

 brane, so that the polar bodies are lost at 

 an early stage. The near equality in the 

 size of the blastomeres also tends to in- 

 crease the difficulties encountered in follow- 

 ing out the details of the cell-lineage. The 

 pilidium with peculiarly short side-lobes, 

 which develops from these eggs, will live for 

 two weeks or more in the laboratory, al- 

 though I have never seen the young nemer- 

 tean develop within it. 



13. Cerebratulus luridus Verr. Specimens 

 collected in Cape Cod Bay by Professor 

 Verrill contained apparently ripe eggs in 

 August. 



14. Carinella pelluelda Coe ripens its sex- 

 ual elements in July at New Haven and 

 Woods Holl. 



15. Parapolia aurantiaea Coe. Genital 

 products mature in August at "Woods Holl. 



16. Valencinia ruhens Coe. A single 

 specimen found at Woods Holl in August 

 1894 was filled with ripe spermatozoa. 



17. Gephalothrix linearis Oersted. At 

 Woods Holl this species commonly ma- 

 tures its genital products in August. The 

 eggs may be artificially fertilized. The 



development is direct and may be readily 

 followed. Mcintosh* has published figures 

 of the embryos of this species. 



The above includes merely those dates 

 at which genital products have been found 

 mature, and should by no means give the 

 impression that they may not be found in 

 some of the species at other times, both 

 earlier and later than is here indicated. 

 The times when the eggs are normally de- 

 posited is certainly liable to considerable 

 variation. Amfhipor^is ochraceus, for exam- 

 ple, has on one occasion been found mature 

 as early as Januarj', although the eggs are 

 produced more abundantly four or five 

 months later. In this respect the nemer- 

 teans agree with many other invertebrates. 

 In some others, as Cerebratulus lacteus, the 

 time during which the eggs can be fertilized 

 lasts for a few weeks at the most, and this 

 period, at New Haven, varies from Feb- 

 ruary to April according to some undeter- 

 mined peculiarity of the season. 



It will be seen that of the common species 

 recorded here nearly all become sexually 

 mature on the southern coast of New Eng- 

 land during the summer months. Only 

 one lays its eggs in mid-winter and only 

 two in the very early spring. 



W. R. CoE. 

 Yale University. 



THE COLUMBIA MEETING OF THE SOCIETY 

 FOB PLANT 3I0BPH0L0GY AND PHYSI- 

 OLOGY. 

 The second annual meeting of this So- 

 ciety was held in conjunction with the 

 meetings of the American Society of Natu- 

 ralists and the Affiliated Societies at Colum- 

 bia University, December 27 to 30, 1898. 

 On the evening of December 27th a reception 

 was tendered to the members of the Society 

 and visiting botanists by the Torrey Botan- 

 ical Club of New York, and the Society 



* British Annelids ; Part I., Nemerteans. Eay So- 

 ciety, 1873. 



