776 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The antenniform hair of Hydrachnida occurs at the anterior end 

 of the hody or, less frequently, on the back, in front of the insertion 

 of the first pair of legs. It is very mobile, and is placed on a small 

 eminence which is hollowed out so as to form a complete socket 

 for its base ; morphologically, it evidently represents the weak hairs 

 which lie at the sides of the orifices of the cuticular glands of the 

 back, as the duct of one of these glands opens close to it. The central 

 canal does not send out fine tubes to the surface, as in the case of the 

 olfactory hairs, but ends blindly; hence the function is probably 

 simply tactile. 



An auditory function is assigned, chiefly by a process of exclusive 

 reasoning, to some very simple long bristles, pointed and pale in 

 colour, which occur at long intervals on the legs. In Eylais a dagger- 

 shaped hair with delicate fringing filaments clothes in great abun- 

 dance the space between the epimerse of the first four legs; it is 

 supplied by a nerve on which a ganglion is placed within the ring 

 which surrounds its base. Some stout, short hairs, placed on the 

 upper edge of the labium in Hydrodroma rubrum, &c, resemble tactile 

 organs, but are possibly, from their position, gustatory. 



The spined elevation of the lower side of the second joint of the palp 

 of Limnesia is, probably, simply intended to meet the opposed claw of 

 the mandible, and is not specially sensory in its properties. The 

 chitinous nail-like tips of the palps of the species of this order, must 

 also be regarded only as grasping organs. 



5. Crustacea. 



Ontogeny of Fresh-water Copepoda.* — J. A. Fric gives (in some- 

 what difficult French) a preliminary note on the ontogeny of fresh- 

 water Copepods, principally confined to the genera Cyclops, Diaptomus, 

 and Canthocamptus. Although it might be thought there was no room 

 for further work in the apparently exhausted field of the anatomy and 

 development of the Copepods, he found on the contrary a considerable 

 number of facts hitherto unexplained. 



The nervous system (brain, oesophageal collar, and ganglionic chain) 

 and the alimentary canal are discussed in detail. In regard to nutri- 

 tion and circulation the author refers to the fact that in this respect 

 the Copepods formed an exception, hitherto unexplained, amongst the 

 Crustacea. The nutritive liquid is set in motion, as is known, either 

 by the heart, or by the regular alternations of the alimentary canal, 

 in cases where the heart is not developed. But the blood-corpuscles, 

 which are so numerous in the Phyllopods, have not, until now, been 

 observed in any Copepod. Claus himself says, " It is remarkable 

 that cellular elements (in the blood) are wanting, whilst they appear 

 in such abundance in the allied Daphnidse, and I have never been 

 able to see blood-corpuscles even in the large, transparent, marine 

 species." 



It is now easy to understand why the lymphatic corpuscles have 

 not been observed in the Copepods : they do not exist in the usual 



* Zool. Anzeig., v. (1882) pp. 498-503. 



