886 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Pycnogonida of the ' Challenger ' Expedition. — Dr. P. P. Hoek's 

 report lately published extends over 150 pp., and is illustrated by 

 twenty-one plates. An interesting general account of a Pycnogonid 

 is prefixed to the catalogue of the species at present known, in which 

 indications are given of the habitat and range of each species. This 

 is followed by descriptions of the forty-one species collected by the 

 ' Challenger,' thirty-three of which are new ; of the nine genera three 

 are new. Those genera which range most widely geographically are 

 also those which range most widely in depth. In an appendix the 

 author gives a valuable sketch of the anatomy and embryology of the 

 Pycnogonida, an account of which is deferred. 



5. Crustacea. 



Hairs of the Anterior Antennae of Crustacea.* — S. Jourdain, 

 after a few words on the auditory hairs of this group, proceeds to 

 point out the arrangement and structure of the processes found on 

 these antennules, which were regarded by Leydig as having an 

 olfactory function. Before describing the arrangements which obtain 

 in the representatives of different orders, he says, that in all cases we 

 find a very delicate chitinous sheath, which is penetrated by an off- 

 shoot from the hypodermic layer, and which, at its base, is found to 

 be in relation with a branch of the antennary nerve ; the free end is 

 truncated and carries a hyaline body, which appears to be comparable 

 to the rods found at the sensory ends of sensory organs. These may 

 be known as the " poils a batonnet." The hairs are cylindrical in 

 some cases, and then the chitinous cylindrical sheath is made up of a 

 number of joints ; the basal ones have thicker walls, and are shorter 

 than those which are more distal. In other cases the hairs are 

 stipifate, and then the joints are ordinarily reduced to three, and the 

 basal one, which is of some length, is constricted in its middle, 



A detailed study shows that the former arrangement is confined to 

 the Podophthalmate Crustacea ; the hairs are found in the young, 

 though in less number than in the adult ; and, similarly, they are 

 more numerous in the higher than in the lower forms. Although 

 there seems to be no doubt that these organs respond to stimuli which 

 are something else than tactile, we are not yet in a position to definitely 

 assert that they have an olfactory function. The author concludes 

 by remarking that the characters of these parts have a value for the 

 systematist. 



Nervous System and Sense-organs of Sphaeroma serratum. t — 

 G. Bellonci describes firstly the different divisions of the brain of 

 this Isopod ; the thu'd segment includes the two lateral oesophageal 

 ganglia at the sides, and below, united by the oesophageal commis- 

 sure, the four sub-oesophageal ganglia concentrated into a single one ; 

 also the seven thoracic connected by the longitudinal commissure, 

 and the seven abdominal ganglia. Among the various nerves which 

 arc described as proceeding from this region, he notices specially tho 



* Jouru. Anat. ct Pliys. (Robin) xvii. (1881) pp. 402-18 (2 pis.), 

 t Atti AccaJ. Liucei Rom., v. (Transuiiti), 1881, p. 228. 



