The British Oceanic ilntomostraca. 19 



dragged through the water at the stern of a boat. It will 

 often be found to collect (besides the small Crustacea) great 

 quantities of medusas, free-swimming annelids, and larvse of 

 many kinds. These (except the medusae, for which no good 

 preservative fluid is yet known) may be put into spirit, and 

 thus kept for examination. 



Setting aside any special interest which these entomostraca 

 may possess for those who give particular attention to them, 

 there are some points in their structure and physiology which 

 are exceedingly curious, and which cannot fail to interest any 

 cc intellectual observer." These are connected chiefly with 

 sexual differences. In the family Harpacticlce the males possess, 

 for the most part, a large vesicular swelling on the upper 

 antenna (see Fig. 1) ; while in the female the antenna is- more 

 slender, and destitute of this appendage. In the Pontellidce 

 and many of the Galanidce the right antenna of the male is 

 provided with a hinge-joint near the middle, for the purpose 

 of clasping ; and above and below the hinge there is a serrated 

 plate which serves to render the grasp more secure. The 

 left antenna of the male, and both those of the female, are 

 destitute of the hinge. In the Pontellidce there is likewise 

 a large pyriform swelling near the middle of the male antenna. 

 This, with serrated plates and hinge, is well shown in the 

 coloured plate of Anomcdocera Patersonii. ' In the two last- 

 mentioned families, the fifth pairs of feet offer also remarkable 

 sexual differences, and afford excellent specific characters ; 

 these, however, are so varied, that drawings of each species 

 would be required to elucidate them. The right fifth foot 

 of Ichthyophorba denticomis is shown at Fig. 4. The curious 

 method of impregnation which obtains amongst the Copepoda 

 has already been mentioned in the pages of the Intellectual 

 Obseevee. It consists in the attachment to the abdomen of 

 the female of elongated cells termed cc spermatophores" or 

 " spermatic tubes." These may often be seen before their 

 emergence from the body of the male. Fig. 5 exhibits a 

 bundle of them attached to the abdomen of the female Temora 

 velox. 



The oceanic species with which we are concerned in this 

 paper, belong to two distinct orders, Cladocera and Copepoda, 

 both of which are well represented in all our fresh- water ponds, 

 the first by the common Daphnice, the second by the still more 

 common genus Cyclops. 



Dr. Baird, in his excellent Natural History of the British 

 Entomostraca, published by the Kay Society in 1849, de- 

 scribes ten marine species of these two orders : — Evadne 

 Nordmanni, Loven; Oanthocamptus Stromii, Baird; 0. furca- 

 tus, Baird ; 0. minuticornis, Muller ; Harpacticus chelifer, 



