OF THE COiMMON NEMATODE OF THE DOGFISH. 



455 



In 1870, Van Beneden (1) stated that "Dr. Mcintosh has 

 found asexual nematodes in the 'liver' of Carcinus mce7ias, 

 which appear to be the young of Coronilla (A^an Beneden)." 



Again, in 1875, Van Beneden (3a) stated that "The ordinary 

 crab of our coasts, Carcinus mamas, is the veliicle of a nematode 

 which becomes a Coronilla rohusta in the stomach of a ray.'" 



Vaullegeard (14) in 1896 reported tlie larva of Coronilla 

 rohusta (Van Beneden) from a number of crustaceans, but stated 

 that it was rare. In addition to Carcinus mcenas, he discovered 

 it in Fortunus marmoratus Leach, Hyas a/roMeus Linnaeus, and 

 Fagurus bernhardus Linnteus, but found only o.io example in 

 each of the last three hosts. Later he found a dozen nematode 

 larv?e in Fortunus depurator Pennant ( = -?*. marmoratus Leach). 



Linstow (9) mentions the discoveries of Mcintosh and Vaulle- 

 geard, and states that the latter distributed the preparations of 

 the larva?, which iiidubitaljly belong to the genus Spiropteriiia 

 ( Van Beneden). 



Experimental, 



Following up the suggestion of Van Beneden, I have attempted 

 to infect the Common 8hore-Crab, Carcinus mcenas, with the 

 lai'Vfe of FrolejJtus scilltcola. 



The results so far have been disappointing, as I have succeeded 

 in obtaining only one larva, which I may reasonably assume to 

 have developed from eggs, taken in with mature females of 

 Froleptus scillicola, on which the crabs were fed. 



During the course of these experiments I have dissected 

 100 crabs, of which 59 were utilised in the feeding experiments 

 and the remainder in control experiments. Of the 59 crabs used 

 in the feeding experiments, 8 were infected with Froleptus larvce, 

 43 larvae being found. Two of tlie 4L crabs used in control 

 experiments were infected, six larvjie being found. 



Owing to the fact that all the larva), except one, found in the 

 crabs used in the feeding experiments were as old or older than 

 those found in the controls, I am bound to conclude that they 

 occurred as the result of natural infection. 



The larva which I presume to be the result of my feeding 

 experiments measured 1*85 mm. The length of the oesophagus 

 was "35 mm., and the proportion oesophagus : total length was 

 1 : 5*28. There was no cuticular collar present, but the tail 

 was bent at an angle to the remainder of the body. 



The older larvae examined varied in length from 10-16 mm. 

 to 20 mm., and the length of the oesophagus from 1*79 mm. 

 to 2'68 mm. The proportion resophagns: total length fluctuated 

 between 1 : 5-09 and 1 : 8-29. 



In the majority of these older Lirvfe the head-end was sur- 

 rounded by the cuticular collar which is so characteristic of the 

 adult worm. Genital oi-gans were absent, as was also differen- 

 tiation at the tail-end. 



