180 MARINE AND FISHERIES 



5 GEORGE v., A. 1915 



of the worm. The few plerocercoids which are found on the mesenteries and in 

 the coelomic cavity average about 1 cm. in length and resemble those found in 

 the ovaries and testes in that they are more distended than specimens from the 

 alimentary tract. The presence of these will be discussed below in connection 

 with the transference of the oncosphere and its further development. A number 

 of cases were met with in which plerocercoids about 1 • 5 cm. in length were 

 protruding into the coelomic cavity through apertures in the intestinal wall. 

 Similar apertures are often caused by the probosces of echinorhynchi, and in one 

 case a plerocercoid was found protruding from one of them together with one 

 of these parasites. Again, in a small number of cases larvse were found with 

 their scolices imbedded in the stroma of the ovaries while their bodies were lying 

 in the ccelomic cavity. Fish No. 2, in the table, harbored only one larva whose 

 scolex was imbedded in the wall of the stomach, the body, about twice as long 

 as the diameter of the scolex, remaining suspended in the lumen of the tract. 

 The scolex was surrounded by a cavity, a little larger than itself, whose diameter 

 was that of the thickness of the wall of the stomach less a thin outer membrane 

 separating the cavity from the coelome of the host; and in this space were the 

 remains of the stomach wall in a comminuted state much resembling digestive 

 debris. In the wall of the duodenum near the pylorus of fish No. 5, there was a 

 similar cavity containing a plerocercoid about 2 or 3 mm. in length, with its suckers 

 invaginated, which condition will be seen below to be normal for specimens of that 

 size. These two cases could be explained by the development of the oncosphere 

 which had not burrowed far into the wall of the alimentary tract, and perhaps 

 the others could be dealt with in a similar way, but the evidence, though quite 

 meagre, seems to point to an active boring by the larva. In this connection, 

 several authors have recorded the wandering of larvse in the tissues of the host 

 and in the coelomic cavity. Those found in the spleen are quite like specimens 

 taken from the liver of the host. The kidney, on the other hand, is infested with 

 small spherical forms with their scolices invaginated as shown in Figs, lb and Ic. 



External Features of the Plerocercoid. 



The larvae are found with or without the scolex or sucker-bearing portion 

 evaginated. In the very young forms, (PI. XIX, Figs, la, b and c) the suckers 

 are constantly invaginated, but when a length of about 1 mm. has been reached 

 the suckers are found evaginated. From that time until a length of 6 or 7 mm. 

 is attained (PI. XIX, Fig. 5) they may be found in either condition depending on 

 the location in the host and the manner of preserving or fixing. From observations 

 of a number of plerocercoids of all sizes from different visceral organs it may be 

 concluded that the sucker region remains permanently evaginated after a length 

 of about 10 mm. has been reached. However, there are exceptions, as many 

 specimens much longer are found with the scolex in the former condition. For 

 example, the scolices of those found in the gonads of the host are protruded where 

 the length of the body ranges from 4-40 mm., the latter being the length of the 

 largest specimen I have yet found. When a fixing fluid is applied to small speci- 



