OF THE COMMON NEMATODE OF THE DOGFISH. 455 



In 1870, Yaii Benedeu (1) stated that "Dr. Mclntosli luis 

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

 wliioli appear to be the young of CoroniUa (Van Beneden)." 



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

 crab of our coasts, Carcinus mtrnas, is the vehicle of a nematode 

 which becomes a CoroniUa robusta in the stomach of a ray.'' 



Vaullegeard (14) in 1896 i-eported the larva of CoroniUa 

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

 that it Avas rare. In addition to Carcinus mamas, he discovered 

 it in Portunus marmoratus Leach, Hyas araneus Linnseus, and 

 Fagicrus bernhardus Linnaeus, but found only o;iu example in 

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

 larvae in Portunus depurator Pennant ( = -P. marmoratus Leach). 



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

 geard, and states that the latter distributed the preparations of 

 the larvae, wliicli indubitably belong to the genus Spiropterina 

 (Van Beneden). 



Experimental, 



Following up the suggestion of Van Beneden, I have attempted 

 to infect the Common iShore-CJrab, Carcinus mcenas, witli the 

 larvae of Proleptus scilUcola. 



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 

 Prole])tus scillicola, on which the crabs were fed. 



During tlie 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 Proleptus larvce, 

 43 larvae being found. Two of the 4L crabs used in conti'ol 

 experiments wei'e infected, six larvae being found. 



Owing to the fact that all the larvte, except one, found in the 

 crabs used in the feeding experiments were as old or older tha,n 

 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 nun. The length of the cesophagns 

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

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

 was bent at an angle to the remaindei' of the body. 



The older larvte 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 oesophagus: total length finctuated 

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



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

 rounded by tiie cuticular coUai- which is so characteristic of the 

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

 tiation at the tail-end. 



