402 SYRIXGOLAIMUS DIGS 



smarigdus is found in algal "incrustations" of the family Ralfsiae, 

 and probably genus Ralfsia. 3 It is very apparent that the nema feeds 

 upon the Ralfsia, for the color and structure of the contents of the cells 

 of this alga are strikingly characteristic, and the intestinal content of 

 the associated Syringolaims not only has exactly the same color, but 

 frequently is otherwise of such a character that it could be derived 

 only from the interior of the Ralfsia cells. Often, however, there are 

 scattered foreign birefringent particles (carbonate of lime) mixed with 

 the ingested food; but these birefringent particles are similar to those 

 found among the filaments of the Ralfsia, and, taking into account 

 the relative size of the mouth parts of the Syringolaim, it is very 

 natural to suppose that some of this foreign matter would be taken in 

 with the food. 



No one had previously explained the precise nature of the mouth 

 organs of Syringolaimus. They consist of three small, arcuate, more 

 or less acute odontia with a spirally outward throw, well adapted to 

 boring and digging (Fig. 1). Now, it so happens that the location and 

 structure of the incrustation formed by the Ralfsia w T ould require 

 digging on the part of the nema in order to obtain food from it, for the 

 Ralfsia incrustation on the snail shells (Alectrion} is usually overgrown 

 with a thick comparatively impenetrable felt of filamentous green 

 algae (Fig. 3) ; hence the Ralfsia can be reached by the Syringolaimus 

 only by digging. 



The snail, Alectrion obsoleta (Nassa), lives between tide-marks and 

 hence twice daily is exposed to the air, and on each such occasion any 

 algal growth on it naturally dries up more or less. Here then is an 

 additional complication hi the environment of the Syringolaim a 

 highly and rapidly variable temperature and salinity. It is reason- 

 able to suppose these unusual circumstances might give rise to a pecu- 

 liar nemic form adapted to the environment. Thus a clue is found to 

 the marked peculiarities of form and structure noted in Syringolaimus. 



3 Ralfsia; fide Dr. I. F. Lewis. 



