PENTASTOMIDA. 



863 



Tardigrades and certain aberrant Acarines such as Phytoptus, 

 and the arrangement of the reproductive organs is like that of 

 many Arthropods. The other features of their anatomy and 



D 



FIG. 570. Young forms of Pentastomum ttenioidcs (after E. Leuckart). a Egg with embryo , 

 b embryo with two pairs of hooked feet, Hf and Hf" ; c larva from liver of rabbit ; G 

 ganglion ; D intestine ; Hd skin glands ; d older larva ; mouth ; .-1 anus ; Gd genital 

 glands. 



of their life-history is however so peculiar that it seems wiser 

 to regard them as an appendix to, rather than an Order of, the 

 Arachnida. 



Fam 1. Linguatulidae with the characters of the order. 



There are three genera. 1. Linguatula Frohlich with a 

 flattened, turbellarian-shaped body, the body cavity extending 

 into the lateral wings which are crenelated at the edge. Species 

 have been found in a fresh-water South American fish Acara 

 and are probably larvae, in the nose and trachea of Fdis onca, 

 in the throat of a Caiman, and the commonest of all L. taenioides 

 in the nasal passages of dog and wolf, the fox, horse, sheep, mule 

 and man ; the larva of the latter has been found in the rabbit, 

 hare, guinea pig, ox, pig, horse and a few other animals. 2. Poro- 

 cephalus Humboldt (Pentastoma Rud). The body is cylindrical 

 with a more or less well developed head. This genus usually 

 inhabits the lungs. It occurs in large snakes, crocodiles, 

 lizards, some birds, e.g. sea-gulls, tortoises and many members 

 of the order Carnivora. 3. Reigkardia, devoid of annula- 

 tions, transparent, with poorly developed hooks but a 

 mouth armature, is found in the air sacs of Bonaparte's Gull 

 and in the common tern of North America. 



END OF VOL. III. 



