Introduction to Animal Morphology. 371 



at the base of the coxopodite, where there are accessory legs 

 for attaching the ova. There is one family, Pycnogonidae, and 

 seven genera ; some are fish-parasites. 



Order 2. Tardigrada (Dujardin} hermaphrodite, minute, 

 worm-like, acardiac, with soft skin; cephalothorax and ab- 

 domen fused ; four obscure metameres, and four pair of short 

 legs, rudimental, each with three or four curved claws ; the 

 last pair of legs terminal ; mouth suctorial, on a fleshy tube, 

 with two salivary glands, and the antennary jaws forming two 

 piercers, with protrusor and retractor muscles ; oesophagus 

 gizzard-like ; stomach large, with many grape-like caeca ; 

 ocelli two ; the single ovary and the lateral testes open into 

 the cloaca ; ventral ganglia are further apart than in the last 

 order. They live in damp moss and gutters, and can bear 

 drying with impunity, like Rotifers. They lay a few large 

 eggs during the moulting process, and the slough acts as 

 an egg sac. There is one family Arctisca. Macrobiotus has 

 no palps or bristles. Echiniscus has marginal bristles. Mil- 

 nesium is palpate, but with no bristles. Emydium has 

 both. 



Sub-class 2. Autarachna (Haeckd) true Arachnids, with a 

 developed abdomen, rarely undergoing retrogression, usually 

 with respiratory and excretory organs, and ova with partly 

 cleaving yelk. Three orders are included : 



Order i. Acarina soft-skinned, with unsegmcnted abdo- 

 men, united to the cephalothorax ; ocelli none or two, rarely 

 more ; respiration tracheal or dermal ; mouth either mastica- 

 tory, with claw-like antennary jaws, or suctorial, the rostrum 



sucking tube being the united pair of mandibular palps, 



Gaining the stilet-like antennary jaws ; ventral cord, with 



Mglion; anus ventral; legs four pair, each with two 



digestive canal simple, or with caeca, which are 



^furcate at their end, sometimes all directed forwards. 



There is no heart nor separate liver (except the grape-like 



i in Trombidium, &c.). Tin- Iracheaj have often feu 



', and one pair of stigmata 



at : of the antennary jaws, or of the third or fourth 



limb-pr: :iing is simple, preanal, often farfor- 



..- 1, and the oviduct is often widened into a uterus. The vas 

 2B2 



