LinncEan Society. 433 



rostral plate is wider than long, but not so wide as in the G. scyl- 

 larus, neither is the tip so much deflexed as in that species. The 

 raptorial legs are rather slender, and are considerably compressed, the 

 base of the terminal joint is very slightly thickened, the terminal part 

 elongated and knife-shaped, the inner edge with two teeth ; tarsi of 

 the three last pair of legs styliform ; abdomen with the lateral mar- 

 gins of the first five segments thin and membranaceous, the fifth vrith 

 a notch at the hind angle ; the sixth segment with six slight crests 

 terminating in short spines, the two middle approximating; the seventh 

 segment with a sharp crest which rises nearly as high above its dor- 

 sal surface, as the space between its base and the edge of the segment ; 

 the end of this crest is pointed ; the marginal teeth of the seventh 

 segment are long and sharp, and have a slight ridge behind; the 

 penultimate joint of the outer branch of the appendages to the sixth 

 ring long, and furnished on the outer edge with a series of nine'spines, 

 which are depressed, and cover each other at the base. In the G, 

 scyllarus there are twelve of these spines. 



This species is about four inches long ; in its dry state the greater 

 part of the upper surface is tinged with a reddish hue, and along the 

 middle of the back there is a pale line. 



The species of the genus Gonodactylus are, — 1. G. chiragra; 

 2. G. scyllarus; 3. G. Edwardsii, Berthold, Act. Gottingen. 1845, 

 t. 3. f. 6 ; 4. G. cultrifer ; 5. G. styliferus ; 6. G. graphuriis ; 7. G, 

 trispinosus. The G. Edwardsii is the species met with in nearly 

 every box of insects and fish imported from China. 



LINNiEAN SOCIETY. 

 June 4, 1850. — Robert Brown, Esq., President, in the Chair. 



Read a " Notice of a peculiar Structure of the Cells on the sur- 

 face of Callitriche verm." By E. Lankester, M.D., F.R.S., F.L.S. 



The peculiar cells described by Dr. Lankester were found by him 

 in the summer of 1849 on the stems of a specimen of Callitriche 

 verna preserved in a glass vessel with other water plants. They 

 project from the surface of the plants, are of a stellate form, and 

 consist of a central cell surrounded by six or eight others. They 

 are easily detached from the epidermal tissue, and may thus readily 

 be procured for microscopic examination. They vary in size as well 

 as frequency, and are not confined to the stem, but occur also on 

 the leaves ; and Dr. Lankester is inclined to believe that they are 

 most abundant in the younger states of the plant. In the first stages 

 of their growth they are to be distinguished from the surrounding 

 cells only by their peculiar arrangement ; but as the development 

 proceeds, the epidermal (including these stellate) cells contain a 

 smaller proportion of chlorophyll than those under and above them 

 on either side of the leaf, and become gradually freer from cell-con- 

 tents, until at last they appear perfectly clear. In other water 

 plants, such as Lemn(e, Potamogeta, &c.. Dr. Lankester had not 

 succeeded in detecting any similar bodies. As regards tbeir func- 

 tion, he states, that it at first occurred to him that they might per- 



