720 



CTENOPLANA. 



bone, came floating by, borne along by a two-or-three-knot current to the north. One 

 of my boys who knew my interest in flotsam, jumped into the dinghy with praiseworthy 

 dispatch and secured the shell. 



It had been afloat long enough to allow many kinds of larvae (Crustacean, 

 Anthozoan, Annelid) to attach themselves to it whether as a temporary resting-place 

 or as a permanent foundation. I placed it in an enamelled basin with sea-water, 

 whereupon many of the organisms detached themselves and swam about in the dish. 

 My attention was soon attracted by some small flattened disc-shaped bodies about 

 one-third of an inch in diameter which could both creep and swim. As they crawled 

 along they jerked out a pair of milk-white tentacles having a worm-like motion of 

 their own, and quickly retracted them, repeating the process continually. My joy was 

 complete when I recognized in these small creatures the very remarkable genus 

 Ctenoplana of which only one specimen had ever been seen before, namely in 1886 

 by Prof. Korotneff, who found it in the plankton or drift-fauna off the coast of Sumatra. 



Although cramped for space in the little cabin of my cutter I had the necessary 

 appliances for making a cursory examination of anything which required immediate 

 attention and was thus able to make some additions and emendations to the account 

 furnished by the original discoverer, and I considered that my re-discovery of Ctenoplana 

 made amends for a great deal of trouble and disappointment. 



FlG. 13. Ctenoplana; (1) from above in attitude of creeping with tentacles extruded; (2) and (3) side- 

 views in attitude of swimming. The first two are the red form, the third is the green variety which contained 

 male gonads; t.o. position of orifice of the sheaths of the pinnate tentacles. (After Willey, Quart. J. Micr. Sc.) 



Ctenoplana is one of those puzzling creatures which rack the brain of the contro- 

 versial morphologist in his futile effort to arrive at a provisional settlement of a point 



