204 BUNTING. [Vor. IX. 
Hydractinia than of the former. However, in the summer of 
1891, Dr. Conklin tells me, that one of his students found 
them in great abundance upon some of the piles! of the Fish 
Commission wharf, but when searched for in the summer 
of 1892, there was no evidence of them remaining. Again, 
two students at the Wood’s Holl Laboratory brought to me 
the shell of AZytelus edulis, and another of Lzmulus, upon 
which colonies were established. I carefully looked over the 
colonies and found that while the nutritive polyps were much 
extended and healthy looking, the reproductive ones were 
small and very immature, although at a time of year when 
the colonies on Pagurus shells were reproducing sexually with 
great activity. The colony, also, contained more of the de- 
fensive polyps in proportion to the other polyps than I had ever 
seen on Pagurus shells. The solution of this problem seems 
very clear, because when there was a choice offered, the 
planulae always showed a marked preference for Pagurus 
shells, while, if by chance, they should have drifted to a place 
where these shells could not be found, they were capable of 
developing upon anything else with which they came in contact. 
The distribution of the colony upon the Pagurus shell is 
very interesting and suggestive. We find situated directly 
around the opening of the shell through which Pagurus 
protrudes, the long whip-like zooids, next to them the 
nourishing hydroids with a few reproductive ones interspersed 
among them, while beyond these, we have the reproductive 
polyps. This massing of the reproductive polyps gives a 
prevailing pinkish tint to the male, and a greenish tint to the 
female colonies. The position of the spiral zooids Weismann 
seems to consider a protection to the crab, in that they prob- 
ably paralyze small animals and prevent them entering the shell. 
On the other hand, my observations lead me to believe that 
Pagurus is of immense service to the hydroid colony, and it is, 
perhaps, particularly due to this fact, that we find the hydroids 
so abundantly distributed upon the Pagurus shell. These 
1Samuel F. Clarke found Hydractinia upon the piles of the wharf at Fort 
Wool, Chesapeake Bay. After close investigation he decided that this form was 
Hydractinia Echinata. 
