u-ith Modern Representatives. 393 



Prom this he infers that in Anaspides, in the Mysidse, and in the 

 Decapods a primary sulcus exists, delimiting an anterior region, or 

 head, to which three pairs of appendages, antennules, antennae, and 

 mandibles belong ^ (the region of the three-paired appendages of the 

 Nauplius, the "primary head-region" of the Crustacea, according 

 to Clans). 



Dr. Caiman has observed what appear to be a group of ' ocelli ' on 

 the head just in front of the cervical furrow ; as no similar larval 

 eyes exist in any known adult Malacostracan, this is indeed a most 

 embryonic character. He is also able to confirm Thomson's discovery 

 of an auditoiy organ in the base of the antennule of Anaspides, a fact 

 of very great interest, such organs having at one time been considered 

 as almost confined to the Decapoda. But the discovery of paired 

 otocysts in the head of certain Amphipoda {Oxycephalus), being 

 regarded by Claus as probably homologous to the auditory organs in 

 the Decapods, he thinks they may have been a character of the 

 primitive Malacostraca, a further indication of the more generalized 

 and primitive type presented to us in Anaspides. 



The compouncl eyes are pedunculated, and placed at the base of the 

 antennules in an emargination of the head which forms a slight 

 rostral prolongation above the eye-stalk. 



The antennules are supported on a stout three- jointed peduncle, of 

 which the first is the longest, while the third joint bears a short inner 

 and a long outer flagellum. 



The antennae, the peduncle of which is composed of two stout basal 

 joints, while a third distal joint bears an elongate-oval, setose scale or 

 exopodite, and also a long multi-articulate flagellum armed with 

 minute spines or bristles. Dr. Caiman describes the mandible, the 

 lower lip (labium or prognatha), the first and second maxilla, and then 

 passes to the thoracic limbs,- the first pair being maxillipeds, the 

 endopodite developed as a stout seven- jointed leg, bearing on its inner 

 face two flattened setose lobes and two branchial lamellae on the 

 outer face of its basal joint, and a rudimentary slender exopodite on 

 the second narrow joint (the basipoclite), the leg terminating in 

 a single claw. 



Each of the four pairs of thoracic legs which follow bears two 

 broad, delicate, oval, branchial lamellae on the coxal joint, and a well- 

 developed, many -jointed, setose exopodite on the second joint of the 

 endopodite, which forms a strong walking-leg fringed with hairs. Of 



' In this arrangement the eyes are apparently not admitted as representing 

 a separate segment, although they have been so considered by Milne-Edwards, Bell, 

 Dana, Charles Darwin, Spence-Bate, Sars & Lang, Huxley, H. "Woodward, and 

 others. Charles Darwin writes : " If that part of the larva in front of the mouth 

 bearing the eyes, the prehensile antennae, and in the earlier stage two pair of 

 antennae, be formed, as is admitted in all other Crustacea, of three segments, then 

 beyond a doubt, from the absolute correspondence of every part . . . the peduncle 

 of the Lepadidse is likewise thus formed" (Mon. Cirripedia, Eay Soc, 1851, 

 "TheLepadidas," p. 25). 



* In Dr. Caiman's figure of Anaspides (Fig. 9, ante, p. 392) the segments are 

 numbered on the assumption that the first is welded with the head, and the free segments 

 commence with the second thoracic somite, thus the number of the thoracic segments 

 would actually be eight. 



