8 PROCEEDiyCS OF THE NATIOJ^AL MUSEUM. vol.53. 



rows or pushes her cephalothorax into the host's flesh until it is com- 

 pletely buried and only the genital segment and abdomen are left 

 on the outside. 



From the sides of the head and anterior thoracic segments horns 

 and processes of various sorts now gi*ow out into the flesh of the host 

 and eventually anchor the parasite so firmly that it can not be re- 

 moved except by cutting away the flesh. The irritation produced by 

 the horns develops a tough membrane or skin immediately around 

 them, which adds considerably to the security of prehension. This 

 tough membrane also envelops the free thorax or neck of the parasite 

 and reaches as far as the real skin of the host. In addition to the 

 horns there also grow out on the front of the head in Pennella, Pero- 

 dermn^ and C ardiodectes curious misshapen warts and excrescences. 

 In Ilaemohaphes there are no real horns but only laminate processes, 

 flattened dorso-ventrally, and the free thorax is reflexed upon itself 

 so that the head points backward instead of forward, and the sides 

 of the cephalothorax and the first two or three thorax segments are 

 prolonged laterally. 



Baudouin writes (1905(?, p. 720) that Lernaeenicus sard'mae is able 

 to cling with its cephalothorax to the vertebral column of its host 

 as a woodpecker clings to the trunk of a tree, which would be still 

 another or fourth method of prehension. He does not explain this 

 prehension any further than to say that it is * * * "de fagon a 

 s'assurer d'un solide point d'appui sur ce poisson tres mobile et tres 

 agile" (the sardine). However, from text figures accompanying his 

 paper we can see that the grip upon the backbone is obtained by the 

 short horns which grow out from the cephalothorax. The anterior 

 horn is curved over ventrally around the ventral surface of one of 

 the fish's vertebrae, the lateral horns are curled into the spaces be- 

 tween this vertebra and the one next to it on either side, while the 

 ventral surface of the parasite's cephalothorax is applied to the side 

 of the vertebra. The horns being cartilaginous and rigid furnish 

 a secure grip, which holds the parasite's head in close contact with 

 the fish's aorta. 



Furthermore, in the case of Pennella, in addition to the tough 

 membrane around the head and thorax, the irritation penetrates the 

 surrounding tissue and causes the formation of an enormous cyst 

 as large as an English walnut or even sometimes attaining the size 

 of a lemon, and having the consistency of cartilage. Inside of this 

 the head and neck of the parasite is often twisted in corkscrew 

 fashion, thereby greatly increasing the difficulty of extracting them 

 uninjured. 



Whichever method of prehension may be adopted by the adult 

 female can not afterwards be broken, but is kept throughout her life, 

 and may even continue longer. The author has repeatedly cut out 



