40 Art. 3.— T. Kalmraki : 



Biology. 



Habitat. — Among the species examined, St. trigonocephala 

 always occurs beneath stones or other sunken materials in the 

 estuary of rivulets, where the water is entirely fresh, during ebh 

 tide. The resting position of the worms, with their ventral 

 surface uppermost, would seem to indicate a negative response to 

 gravity, since when moving they may be in an}^ position, depend- 

 ing upon the particular surface over which they happen to l>e 

 gliding. The worms are very sensitive even to a slight irritation. 

 The specimens contained in a glass dish, when jarred even 

 very slightly, instantly stop, contract and remain immovable. 

 They usually wander to a dark place. It is due perhaps to this 

 property that the parasitic planarians never willingly leave their 

 host animal. 



In the course of the past year six parasitic species were 

 recorded, which may be divided into two categories according to 

 their relations to the host, viz., permanent parasitism and com- 

 mensalism (pseudoparasitism). The species brought under the 

 category of true parasitism is Micropharynx parasitica Jägerskiöl]) 

 (32), wdiich lives attached to the dorsal surface of the body of 

 Raja clavata and batis. Regarding the habits of this species, 

 however, no further report has, up to the present, appeared. The 

 species Ijrought under the category of commensalism are the 

 worms which attach themselves firml}- to the cephalothoracic 

 appendages or to the gill-books of Limulus, such are Bd. Candida, 

 Bd. icheeleri, Bd. propinqua, Syncoelidium pelhfcidum and I'Jct. 

 limidi. In general, these worms have long been regarded as true 

 parasities whicJi bring about the fall of the cephalothoracic ap- 

 pendages as well as of the gill-leaves, injuring the skin of the articu- 

 lation. WiLiiELMi (69), however, has considered the question from 

 a purely experimental point of view, and has come to the conclu- 

 sion that these worms are not true parasites of Limulus. TYiqj (\o 

 not apparently feed on any part of the host's bod3^ So far as I 

 have examined, any trace of injury caused by the parasites could 

 nowhere be found on the skin of the articulation of Limulus. 



