484 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [32] 



applied to their heads. This was characteristic of those of the first lot. 

 With those found in the spiral valve, however, the case was quite 

 different. In it these parasites were found to be firmly attached to the 

 wall of the intestine. Many of them had tunneled holes in the mucous 

 and submucous coats. In some cases these tunnels cut through the 

 muscular coats of the intestine and opened into the interior body cavity. 

 In some instances several heads were found occupying the same cavity. 

 One of these pockets was 6.5 mm deep. In it were imbedded three heads 

 belonging to three strobiles 20 mm , 32 mm , and 55 mm long, respectively. 

 The heads were so tightly fastened in their fleshy cavern that they had 

 to be cut out before they could be removed. A peculiarity of the in- 

 dividuals of this second lot is a tendency to contract the anterior seg- 

 ments, so that instead of being attenuated as in most of those of the 

 first lot, the anterior segments are at first nearly as broad as the neck, 

 and immediately widen until they are as broad or even broader than 

 the head. This gives the worm the appearance of being constricted 

 just back of the head. This habit of tunneling into the flesh of its host 

 must make this parasite a very unpleasant guest. Usually in the case 

 of those Cestoidea which infest the alimentary canal of their host, their 

 presence cannot give rise to much pain, unless they are present in 

 numbers sufficient to occasion obstruction. But with this worm it is 

 quite otherwise. Wherever tunnels in the walls of the intestine caused 

 by this worm were observed, it was noticed that there was much irrita- 

 tion of the mucous membrane. Not only was the mucous coat highly 

 inflamed, but the inflammation often extended into the submucous and 

 muscular coats. The whole interior of the spiral valve was blotched 

 with angry-looking sores. If this is at all common, then we find in 

 this worm an enemy of the Dusky Shark, small but not insignificant. 

 It is certainly encouraging to find in nature, in the too small army of 

 enemies which are arrayed in warfare against the Selachians, these 

 humble sappers and miners lending their aid towards keepiug down the 

 numbers of these Ishmaelites of the sea. 



Abnormal forms. — In the second lot a few monstrosities were ob- 

 served, two of which are figured (Plate IV, Figs. 21 and 22). The 

 iirst example, Fig. 22, is a strobile 13 mIU in length, which, at about 2 inm 

 from the posterior end, gives off from the x^ostero-margiual edge a sec- 

 ondary strobile, in which there aro about four joints faintly marked. 

 The dimensions of the segment which sends off this budding part are: 

 Length, 0.1 mm ; breadth, 0.72 mm ; of the succeeding segment, length, 

 ().l mm ; breadth, 0.62 mm ; of the budding portion, length, 1.08" 1 " 1 ; breadth, 

 0.0G mn \ The second example, Fig. 21, is a fragment; length of strobile 

 not known. The segments have the beginnings of the male genital 

 organs. A secondary strobile is given off from the margin of the pri- 

 mary strobile in a somewhat different manner from the one just de- 

 scribed. A tendency towards a marginal thickening can be seen on the 

 third segment in front of the one from which the secondary strobile 

 becomes free. In the succeeding segments this marginal thickening, 



