No. 5.] THE HABITS OF PYCNOGONIDS. 205 



roll up into separate balls, for I have had opportunity to observe 

 them for only a few days after they were laid ; but this does not 

 seem to me probable. 



Cases of the males carrying the eggs are rare among animals 

 and occur in widely separated groups; the male of the obstetric 

 toad (Alytcs obstctricans] winds the egg-strings about his body 

 and carries them till the tadpoles hatch ; the male of a South 

 American frog (Rhinoderma darwinii] takes the eggs into his 

 vocal sacs to develop ; and the males of some of the Lopho- 

 branch fishes have brood pouches for the reception of the ova. 

 In looking over the literature I have been unable to find any 

 reference to this habit among the invertebrates, aside from the 

 whole group of Pycnogonids. It seemed a matter of consider- 

 able interest to know just how such a seemingly intelligent act 

 as the transfer of the eggs to the male takes place in animals 

 whose movements in general seem to exhibit so low an order 

 of psychic development, and I kept close watch of them with 

 this point in view. So far as I am able to ascertain, the 

 process has never been described, though Hoek 1 gives an account 

 of the copulation in a European species as follows : " In 

 regard to the way in which the eggs are laid, I had the 

 good fortune to observe the copulation of a male and female 

 PJioxichilns laevis Grube, when I was, last summer, in the 

 zoological station of Professor H. de Lacaze-Duthiers at Ros- 

 coff. The eggs are fecundated the moment they are laid, and 

 the copulation, therefore, is quite external, brought about by 

 the genital openings of the two sexes being placed against 

 each other. Half an hour after the beginning of copulation, the 

 male had a large white egg-mass on one of his ovigerous legs, 

 and about one hour later both masses were present." Only 

 once, on August 16, at 6.15 A.M., was I fortunate enough to 

 observe the pairing of Anoplodactylus. When first noticed 

 both animals were among the hydroids ; the male was clinging 

 to the dorsal surface of the female and headed in the same 

 direction. Both animals were kicking slowly in an indefinite 

 sort of way, but gradually the male drew forward and, 



1 Iloek, P. P. C., "Report on the Pycnogonida, dredged by H. M. S. Chal- 

 lenger during the years 1873-76," Challenger Reports. Zoology, vol. iii, p. 131. 



