IF YD K \rllNA. 261 



in harmony during captivity, I was induced to name the crea- 

 ture ll'1'lrni-hiin jJ'ti-iifn, a character so opposite to that which has been 

 derril>ed. Plate I.XYIII . enlarged, fig. 29.* 



llydrachiue sometimes subsist spontaneously on other animal dub- 

 stances. When I'eedini: profusely, they are full, plump, and smooth, of 

 velvet appearance, and remain so after death. Owing to tin- extreme 

 difficulty of olitaining correct delineations of such active and restlew 

 animal-, it is probable that most of the figures preserved have been those 

 of specimens after life had fled. All the illustrations presented here. 

 however, were taken from animals during vigorous animation. N> 

 theless, the characters of many an- most equivocal. 



The llydnicliiuo breed at different periods of the year, and, in com- 

 mon with the smaller insects, cliietly during summer. Conspicuous indi- 

 cations of sex were noted long ago by Miiller, and more recently also by 

 M. Duges. But there are species wherein the difference is extremely 

 slight, though no resemblance between the male and female exists in 

 others. 



During the union of a species of the .S'//// ///, the pair remained 

 motionless at the bottom of their vessel. Spawn appears in April, and 

 during the subsequent month, and the maturity of the young has l*-en 

 also postponed as late as the beginning of November. 



Certain species of Hydrachnse are extremely prolific. Some of those 

 above enumerated, such as the Ht/Hrachna i-.it, '/>, allixetl more than 

 six hundred ova to the side of a glass jar, where its history could be 

 favourably and distinctly followed. The quantity and fashion of tin- 

 deposit depends much on the species ; it is generally in patches, and the 

 same spot being resorted to repeatedly by the parent, it occasionally at 

 tains considerable dimensions. 



The patches consist of twelve, twenty, an hundred and fifty, or a 

 greater number of ova, for the most part symmetrically arranged in a 

 single stratum, on leaves, wood, stone, or whatever else may have been 



* Body, tending to globular, about half a line in diameter. Eye*, two on the anterior 

 surface, black, considerably apart. Limbs with scanty hairs. Colour grayish-brown, 

 lighter on the middle of the back. Taken in a small pond on Braid Hill*. 



