366 



ANDROGYNOUS MOLLUSCA. 



tine, distinguished from the latter by its insolubility in 

 water, and by affording no precipitate with solutions con- 

 taining tannin ; and from the former by not coagulating on 

 the application of acids or electricity, and by forming com- 

 pounds with the alkalies which are not saponaceous. It is 

 sufficiently tenacious to adhere with firmness to the leaves 

 and stones on which it is deposited, and compact enough to 

 retain its form. This is usually oval or linear-oblong,* but 

 sometimes the figures are more artificial. Messrs. Alder and 

 Hancock have figured the spawn of many Nudibranches, 

 which is often laid in coils, modified in character in different 

 species. You have here the representation (Fig. 76) of a 



Fig. 76. 



characteristic example in the spawn of a large Doris, for 

 which I am indebted to Mr. Cock of Falmouth. I once 



the egg a little patience will bring the heart in full view again, and that as 

 long as the embryo continues within the egg. Nay, even after it is hatched, 

 the heart may be discovered for some days through the transparent shell.'' 

 Employm.Jbr the Microscope, p. 325, 326. 



* The eggs of the Ampullaria, an exotic genus of fresh water shells, are 

 in the form of little rounded vesicles, often agreeably coloured with green 

 and clustered in groups upon the stalks of aquatic plants. RANG, Man. 195. 

 See the Ray Rep. on Zoology, 1845, p. 120, for a description of the egg- 

 capsules of Valvata piscinalis. 



