168 



SCIENCE. 



[N. S. Vol. IX. No. 214. 



Several other species of Tetrastemma and 

 AmpJdporus have been found mature in mid- 

 summer. 



5. Emplectonema giganteum Verr. has been 

 found by Professor Verrill with large eggs 

 in August. 



6. Lineus viridis Johnson = L. gesserensis 

 Miiller = Nemertes obscura Desor = Lineus 

 obscurus Barrois. On the Coast of Maine 

 Verrill* has found the eggs of this species 

 very abundant iiuder stones at low-water 

 mark. These were imbedded in mucus and 

 were deposited in mid-summer. At Woods 

 HoU during three summers I have exam- 

 ined thousands of specimens but have found 

 no eggs. On the northern coast of Eui'ope 

 the eggs are mature from March to 

 May. The development of this species 

 was studied by Desorf as early as 1848 

 from material which he collected near Bos- 

 ton in February. BarroisJ and, later, 

 Hubrecht§ have published detailed descrip- 

 tions of its embrj'ology. 



7. Lineus soeialis (Leidy) Verr. The 

 eggs mature in mid- winter at New Haven, 

 and are sometimes deposited in captivitj^ in 

 masses of mucus. They develop readily at 

 least to the stage of swimming gastrula?. 



8. Lineus bieolor Verr. Specimens dredged 

 in Vineyard Sound in July, 1898, contained 

 mature genital products. 



9. Mierura affinis'Verr. Specimens taken 

 off Salem by Professor Verrill contained 

 fully developed eggs and spermatozoa in 

 mid-summer. 



10. Micnira ececa Yerr. Matures its geni- 

 tal products at Woods Holl during August. 

 The eggs of this species are beautifully 

 clear and transparent and develop readily 

 when artificially fertilized. The cleavage 



* Trans. Connecticut Acad., Vol. 8, 1893. 



f Boston Journ. Nat. Hist., Vol. 6, 1848. 



JEeelierches snr I'embryologie des Nemertes. 

 Lille, 1877. 



§ Proeve eener Ontwikkelingsgesohiedenis van 

 Lineus obscurus. Utrecht, 1885. 



is of the regular spiral type, of which these 

 eggs furnish an almost ideal illustration. 

 The pilidium which results will live two 

 weeks or more in confinement. 



11. Cerebratulus lacieus Verr. The eggs 

 are ripe at New Haven during February, 

 March and April. On the coast of Maine 

 the species is said to breed in early summer. 

 I have never observed that the eggs are de- 

 posited in captivity. Specimens filled with 

 eggs have been kept alive in the laboratory 

 for more than two months after the time 

 of full maturity of the sexual products 

 without discharging their eggs. Whether 

 they would be capable of normal develop- 

 ment after this length of time I was unable 

 to determine, because all the males which 

 could be obtained had long since discharged 

 their spermatozoa. The worms attain an 

 enormous size (up to 22 feet in length and 

 an inch in breadth, according to Verrill) 

 and consequently produce an immense 

 number of ova. I should estimate the 

 number to be obtained from a fair-sized 

 worm — say, 5 feet long — to lie between 

 fifty thousand and a quarter of a million. 

 A single individual, or even a small frag- 

 ment, will thus furnish all the material 

 required for an elaborate investigation. The 

 eggs are easily fertilized artificially, and 

 will develop into the pilidium-stage without 

 difficulty. 



12. Cerebratulus Leidyi Verr. Breeds 

 commonly at Woods Holl in July and 

 early in August. In 1898 the majority of 

 the individuals which I found at Woods 

 Holl had discharged their genital products 

 earlier than July, and in 1894 a few speci- 

 mens at New Haven retained their ova as 

 late as October. Among the nemerteans 

 that I know, the eggs of this species are 

 equalled in beautj' and regularity of de- 

 velopment onlj' by those of Micrura cceca. 

 The first division occurs about one hour 

 and ten minutes after fertilization, or in .55 

 minutes if the eggs have been allowed to 



