90 ARTHROPOD A. 



These are mostly spider-like, marine animals, very sluggish, and 

 some of them external parasites. They have four ocelli, no 

 antennae, and a rostrate head, with a mouth either with or with- 

 out mandibles and palpi. In Nymphon the digestive tube sends 

 a branch into each limb, which are, according to Milne-Edwards, 

 the seat of a peristaltic motion. Johnstone asserts that the heart 

 also sends a branch into each limb. The females are known by 

 having a pair of spurious legs for the purpose of carrying the 



The earlier states are not well understood ; but there appears 

 to be first a naupliiform state, the larva afterwards losing its 

 three anterior pairs of appendages. [In the Crustacean Nauplius 

 these three pairs always represent the antennary and inandibular 



From their tegumentary respiration, having no tracheae or 

 pulmonary sacs, Milne-Edwards considers that they have more 

 analogy with the lower forms of Crustacea, which are similarly 

 conditioned. A. Dohrn denies their being either Arachnida or 

 Crustacea. They are now generally placed with the Arachnida. 

 Hackel at one time combined them with Arctisca to form his 

 subclass " Pseudarachna ;" but the latter he now places with the 

 Worms ; the Podosomata he retains in the Crustacea. 



Pycnogonidce. Kymphonidce. Ammothea. 



Pasithoe. Nymphon. Phoxichilidium= 



Phoxichilus. Zetes. Orithyia. 



Pycnogonum. Achelia. Pallene. 



Oomerus. 



Class II. MYEIOPODA. 



MlTOSATA. 



Head distinct ; thorax and abdomen not differentiated, divided 

 into numerous segments [somites]. Two antennae. Feet always 

 more than eight pairs in the adult. Eespiration tracheal. No 

 metamorphosis. 



Although there is no metamorphosis, the young have fewer 

 segments, and three to six pairs of legs or none, but with each 

 successive moult the number is increased. The mouth is com- 

 plex, two pairs of feet sometimes enter into its composition ; the 

 mandibles are jointed. The eyes are simple or compound, in one 



