FRESH-WATER NEREIDS FROM THE PACIFIC COAST AND HAWAII. 215 



designated as "rudimentary" in L. quadraticeps, as Gay ('49, p. 25) has done. 

 Specimens of this species from Punt a Arenas, kindly sent me by Dr. Michaelsen, 

 possess a dorsal cirrus, small indeed but not "rudimentary." The entire foot is 

 very small in this species. In no known species is there the least trace of a dorsal 

 or ventral ligule. The dorsal ramus in all is extremely rudimentary; in some (L. 

 geayi, L. senegalensis, and L. littoralis) it is a mere setigerous knob on the upper side 

 of the ventral ramus; in others (L. ouanaryensis, L. abiuma, L. quadraticeps, and 

 L. brevicornis) it is represented only by one or more setae and the aciculum; finally, in 

 L. hawaiiensis nothing remains but the aciculum. The retractile tip of the foot, appar- 

 ently a constant character of this genus, has already been described. (See p. 211.) 



Horny jaws are present in all species of Lycastis, the number of teeth varying 

 from 4 in L. senegalensis to 20 in L. geayi. In no species are there any paragnaths, 

 or even soft papillae, on the proboscis. This absence of paragnaths, however, is not 

 peculiar to Lycastis, but is shared by Lycastoides, Ceratocephale, and Dendronereis. 



It remains to be discovered whether the extensive system of intraepidermal 

 blood-vessels present in L. hawaiiensis is characteristic of the entire genus. 



The most remarkable physiological character of the genus is the facility with 

 which the different species establish themselves in fresh and brackish water. No 

 fewer than five of the eight known species have fresh-water or brackish-water habi- 

 tats. Not one, however, lives remote from the sea, and, with the possible exception 

 of L. hawaiiensis, not one is known to be landlocked. In two instances, at least, 

 the forms have a wide range, extending from a purely marine environment, through 

 brackish water, to fresh water. L. quadraticeps (Ehlers, '97, :01) and L. ouanaryensis 

 (Gravier, : 01) are the best instances of tlu's extreme euryhalinism. 



Apparently the sexes are usually distinct in Lycastis. At least no instance of 

 hermaphroditism has been reported. I find, however, that the specimens of L. 

 quadraticeps received from Dr. Michaelsen are all hermaphrodites, containing in the 

 same segment both ova and spermatozoa. The species is minute, certainly one of 

 the smallest of the Nereidse, as my largest specimens do not exceed 25 millimetres 

 in length and are scarcely 1 millimetre in transverse diameter. The ova are very 

 few and immensely large for the size of the animal. There is usualty but one ovum 

 in each somite, seldom two, and very rarely three. By no means every somite con- 

 tains ova. There is always a considerable but variable number of anterior somites 

 that have none, and a smaller but also variable number of posterior somites that are 

 also without them. The spermatozoa always extend a few somites further cephalad 

 and caudad than the ova. 



