COLE. [VOL. II. 



Marine Biological Laboratory at Woods Roll, and at the sug- 

 gestion of Dr. S. J. Holmes, to whom I am also indebted for 

 much help and advice, I undertook to ascertain something of 

 the habits and reactions of the forms found there. The present 

 paper embodies some of these observations, which though far 

 from complete seem to be of interest. I hope to be able later 

 to supplement them by a more comprehensive account of the 

 biology of the group. Much of this work is rendered difficult 

 by the fact that the animals are not easy to observe under 

 natural conditions. 



As has been noted by Morgan and other authors, there are 

 three species of Pycnogonids to be found at Woods Roll, repre- 

 senting as many genera. These peculiar animals may be found 

 in nearly every collection of hydroids made from the piles or 

 dredged up from the bottom, their long legs appearing to be 

 hopelessly tangled among the stems of the hydroid as they kick 

 slowly about in an aimless but persistent fashion. Perhaps the 

 commonest of these, and by considerable the largest (extent 

 40 mm. to 50 mm.), is the dark purple colored Anoplodactylns 

 Icntns Wilson (= Phoxichilidium inaxillare of Morgan and 

 others), which is especially abundant in colonies of Euden- 

 drium taken from the piles. A smaller species of a yellowish 

 color, Tanystylum orbiculare Wilson, measuring about 7 mm. 

 in extent, was found fairly abundant in a yellowish hydroid 

 almost the exact color of the Pycnogonid. Anoplodactylus was 

 on no occasion found among the light-colored hydroid, nor did 

 I ever find a specimen of Tanystylum among the dark colonies 

 of Eudendrium, where Anoplodactylus is fairly inconspicuous, 

 though I have found the latter among the much lighter colored 

 Bugula growing near the Eudendrium. I am not prepared to 

 say that this is a case of color adaptation, as my observations 

 were too limited to confirm this view, but merely throw out 

 the suggestion for what it is worth. And it is worth remarking 

 in this connection that the third representative occurring in 

 this locality, Pallenc brevirostris Johnston (=P. empusa Wil- 

 son), which is a slender whitish or more or less transparent 

 form and is very hard to see for this reason, was found to be 

 much more generally distributed than either of the other 



