PECULIAR HABITAT OF A PYCNOGONID. ip/ 



the Tortugas in 1906, I myself obtained a live specimen of 

 Endeis spinosus, the animal appearing in a finger bowl which 

 I had just filled with sea water by means of a hand pump used 

 for that purpose, thus showing that the pycnogonid must have 

 been swimming freely in the water when it was sucked in by the 

 pump. Whether these pycnogonids which were taken at the 

 surface had merely become accidentally detached from their 

 regular abodes, or whether certain species naturally swim freely 

 in the water at certain times, I am not prepared to say. 



In the present connection the reaction of certain pycnogonids 

 to light is of considerable interest. I have shown (Cole, 1901) that 

 Anoplodactylus lentus and Pallene brevirostris, both of which can 

 sustain themselves in the water by swimming,^ move uniformly 

 toward a source of light of moderate intensity (diffuse daylight). 

 I was, furthermore, able to prove the same thing for Endeis, 

 at least for the one specimen mentioned above as secured by 

 myself at the Tortugas, the reaction being in all respects similar 

 to that previously described for the other genera. The biological 

 significance of this reaction in the case of Endeis, living among 

 the hydroids on the gulf -weed, is at once apparent, for any in- 

 dividual which by chance became detached from the hydroid 

 would, in response to the light coming from above, swim upward 

 instead of going down into the deeper water, and would in this 

 way stand a much better chance of again finding suitable attach- 

 ment. From the fact that the young of all stages appeared to 

 be clinging as tenaciously to the hydroids as the adults, I am in- 

 clined to believe that they probably do not have a definite free 

 swimming stage, but swim only when circumstances make it 

 necessary. 



The newly hatched larvae possess strongly developed chelifores 

 and stout chelae by which they attach themselves to any avail- 

 able object. Normally they remain clinging to the egg cluster 

 on the legs of the male for some time after hatching. The use- 

 fulness of these effective grasping organs is readily apparent, 

 since without them the larvae would almost inevitably become 

 detached and lost from their floating abode. I have elsewhere 

 (Cole, 1904, p. 316) pointed out the usefulness of the chelifores 



' The " swimming " consists simply of a vigorous kicking. 



