11 



The Pentastomida {Pcntastunta or Linguatula, &c.) are curious 

 worm-like creatures (see Fig. 12), of doubtful affinities, usually 

 considered to belong to the Arachnid group, i.e. to be allied to 

 Spiders and Mites. But in general appearance they resemble 

 worms, having a comparatively soft elongated body, without limbs, 

 and the head being armed with two pairs of sharp, horny hooks. 

 In their immature stages they may occur enclosed in cysts among 

 the tissues of almost any part of the body, and in almost any 

 Mammal or Bird, or living free in its various cavities, more 

 especially the general body-cavity. The adult forms usually occur 

 in Snakes or other carnivorous Eeptiles, and mostly take up a 

 position in the lungs of their host. 



Parasitic Crustacea of various sorts may also occur. They 

 are found mostly on Fishes and Whales, or on other Crustacea, 

 on Mollusca and other aquatic invertebrates ; they may assume a 

 very different appearance from a typical Crustacean. The iDody 

 may be reduced to a mere soft sac, w^ithout appendages, or with 

 only vestiges of them. Sometimes there is a pair of elongated 

 bags of eggs attached to the body, and looking almost like a pair 

 of legs, or like a pair of long strings. These parasites are very 

 commonly found, for example, clinging to the gills of Fishes. 



Any of the above-mentioned creatures may be safely treated 

 by ordinary methods of killing, such as corrosive sublimate, and 

 preserved in alcohol. 



Insect-larvte may l^e killed by inmiersion for a few seconds only 

 in boiling water, and then placed in weak spirit, in which they are 

 to remain till hardened (two or three weeks). They can finally be 

 transferred to stronger spirit. 



HABITAT OF WORMS. 



The following is intended as a rough indication of what may 

 be looked for in a particular kind of locality, though it is impossible 

 to give a complete guide : — 



(i) Inland localities. 



(a) Parasitic worms. — -Any kind of mammal, bird, reptile, 

 amphibian, or fresh water fish may be found to harbour 

 parasites of many kinds. Nematodes, Trematodes, 

 Cestodes, and Acanthocephala occur in all these 

 groups of animals, either in their laiTal or adult stages. 

 As a rule, dissection is the only method of obtaining 

 them, a special search l)eing made in the alimentary 

 canal. But some of the Trematodes attach themselves 

 to the skin of Fishes. Leeches are sometimes found 

 adhering to animals (e.g. Frogs) which have I'ecently been 

 in or near water. Reptiles, especially Snakes, are some- 

 times found to harbour Pcntastoma (or Poroccphalus, see 



