118 SELECTED NOTES FROM 



are two or more in number, and the family Cecropidce, with the 

 genus Cecrops as the type, when only one plate exists. They are 

 all parasitic upon marine fishes, and the fishermen commonly call 

 them fish-lice. ^^ 



H. E. Freeman. 



Caligus. — I am rather surprised that although several members 

 have well described the Caligus^ or " fish-louse," no one has 

 explained, for the benefit of the unlearned, that it is really a 

 Crustacean^ not an insect like the louse, nor an arachnidan like the 

 mites. 



H. F. Parsons. 



Cidaris (spines of). — This slide introduces us to one of the 

 last surviving members of a once numerous family. The genus 

 Cidaris was very abundant in oolitic and cretaceous times, but few 

 living representatives now remain. Cidaris and its allies differ from 

 Echinus in the mode of articulation of the spines to the tubercles. 

 In addition to the capsular ligament there is a central ligament, 

 which is inserted into a little pit on the summit of the tubercle, 

 like the " ligamenhim teres " of the hip joint ; this, however, is 

 not shown in the specimen before us. Pedicellaria with long 

 stalks may be seen among the spines. The spines of the fossil 

 species are very like the present specimen, but larger, some six 

 inches in length. 



— H. F. Parsons. 



Santonine. — A neutral crystalline substance, obtained from a 

 species of Artemisia^ allied to the Wormwood. It is not an 

 alkaloid, like quinine and morphia, for it contains no nitrogen, 

 its formula being C15, H,8, O3. This slide has, I believe, been 

 prepared by fusion. I have got a similar appearance by spread- 

 ing a thin layer of melted santonine on a slide and touching it in 

 a number of places as it cooled. When deposited from hot spirits 

 santonine crystallises in prisms, most of which appear of a steel 

 blue by polarised light. 



H. F. Parsons. 



Santonine is most easily prepared as a polariscope object by 

 dissolving it in chloroform and then evaporating a few drops on a 

 glass slide. If the slide is previously heated, and the solution be 

 dropped upon it, floriated and radiated crystals are obtained, and 

 the forms vary according to the amount of heat to which the slide 

 has been subjected. Fusing santonine does not answer, as most 

 of the substance evaporates. C. F. Tootal. 



