218 NATURAL HISTORY. 



" In general, it is only the adult female of the Lerneaclse that we are in the habit of observing 

 and in an animal whose organs of motion and perception for the most part are merely rudimentary, 

 and whose existence is strictly stationary, the manner of life must be very simple. Immovably fixed 

 upon the fish which serves it for food, its existence depending upon the life of its host, it requires 

 neither feet to transport it from place to place, nor eyes to guide it in search of fresh abode?. 

 In fact, the whole of its active existence consists in. the two operations of taking food and propagating 

 its species. We find them in all instances deeply fixed in the tissue of the parts upon which they 

 have taken up their habitation, and often so deeply lodged that little else but the oviferous tubes are 

 visible externally. These small parasites have been found adhering to the gills of the Dory, the Sole, 

 the Gurnard, and the Salmon, to the fins and gills of the Cod, Haddock, and Whiting, and to the 

 sides of the Carp, Bream, and Roach." 



Scoresby, the Arctic voyager, mentions a species of Lenieopoda found adhering to the eye of a 

 Greenland Shai-k ; the arm-like appendages were buried in the cornea, to the depth of nearly a fourth 

 of their length. The Sharks thus attacked seem to be rendered blind by their pigmy assailants 

 "The sailors," says Captain Scoresby, "imagine this Shark is blind, because it pays riot the least 

 attention to the presence of a man, and is, indeed, so apparently stupid, that it never draws back 

 when a blow is aimed at it with a knife or lance." 



The " Eye-sucker " (Lerneorietna spratta) is found fixed by the snout to the eye of the Sprat. 



Conrad Gesner, in his " Historia Animalium," 1558, describes the structure and appearance of 

 this parasite, " because," he says, " few people know what this parasite is, as it is very small, seldom 

 to be seen, except at the time of the rising of the dog-star, and then not on many fishes, but only on 

 the Tunny, Sword-fish, and occasionally the Dolphin (and not even on every individual). Tt adheres so 

 firmly that it cannot be removed without tearing it. It sucks the blood of the fish, like as a leech 

 does, till it falls off through very fulness, and then dies." 



SIXTH LEGION. CIRRIPEDIA.* 

 ORDER XII. RHIZOCEPHALA (ROOT-HEADED CRUSTACEA). 



In the RHIZOCEPHALA the young are free, and resemble young larval Cirripedia, or the adult 

 Cypris and Candona (Fig. 39). The adult (female) is destitute of all appendages, and attaches itself 

 by means of root-like prolongations from the head to the body of the host upon or within which it is 

 found. 



Thus the female of Entoniscus resides within the body of a species of Porcellana, lying in a thin- 

 walled sac between the liver, intestine, and heart, and is destitute of eyes or antenna?. The thorax 

 has become an irregular inarticulate sac, beset with enormous brood-laminae ; the long vermiform and 

 extremely mobile abdomen has sword-shaped legs ; and swelling out above it in a glandular form, 

 as if in a hernial sac, the heart lies at the base of the first segment. 



The young in this singular parasite closely resemble those of Bopyrus and Cryptothyria. 



The genera Sacculina and Peltogaster are usually found parasitic on the abdomen of the Hermit 

 Crab. The animal appears as a small ovoid or kidney-shaped mass, attached by the head, whilst its 

 roots penetrate deeply into the liver of the Hermit Crab. 



The only manifestations of life which these most retrogress! vely metamorphosed Crustaceans 

 present are powerful contractions of the roots, and alternate expansion and contraction of the body, 

 causing water to flow into the brood-cavity, to be again expelled through a wide orifice. 



In 1858 Lilljeborg found what he deemed to be a female Peltogaster with an egg-sac; but a 

 careful dissection led to the discovery that another parasite of a higher order, namely, a Cryptothyria, 

 had become parasitic upon the parasite. The most curious part of this super-parasitic history is 

 that the roots of Sacculina and Peltogaster seem constantly to be made use of by two parasitic 

 Isopods namely, a Bopyrus and the Cryptoniscns planaroides. These take up their abode beneath 

 the Sacculina, and cause it to die away by intercepting the nourishment conveyed by the roots : 

 the roots, however, continue to grow, even without the Saccitlina, and frequently attain extraordinary 

 extension, especially when a Bopyrus obtains its nourishment from them (Fritz Miiller). 



Let gardeners take a hint from this, and graft some new fruit upon the mistletoe bough. 

 * Latin, cirrus, a curl, and pes, a foot ; hence, curl-footed. 



