26 



INTRODUCTION TO CKYPTOGAMIC BOTANY. 



meutioned may be examined profitably in Phsenogams, but 

 always with more difficulty, and seldom with such precision or 

 with such satisfaction and conviction to the observer, and 

 there is one point which must always be borne in mind, that the 

 objects in question grow and are developed under his eyes, if he 

 possesses proper powers of manipulation, which will scarcely 

 ever be the case with Phaenogams, if the parts be freed ever so 

 neatly from the surrounding tissues* Nay, the examination of 

 the developement of cells in such genera as Hcematococcus 

 and Glceocapsa (Fig. 10) will help even the Zoologist, for no- 

 thing can be more close than the mode of development in these, 

 and of the vitellus in the eggs of certain Mollusca (Figs. J 1, 12). 



Fig. 11. 

 Eggs of Acteon viridis in different stages. 



a. Egg, showing the vitellus still simple. 

 h. Egg, with four celled vitellus. 



c. The vitellus divided into two. 



d. Ditto into four. 



From Vogt Reoherchea sur I'Embryogfinie des MoUusques Gasteropodes, 

 Ann. d. So. Nat., ser. iii. vol. 6, p. 1. 



The bodies, indeed, which are so much aUke, or in other 

 words are homologous, identical, that is, in structure and 

 genesis, though not in function, may not always be of equal 



* Most eminent vegetable Physiologists have been more or less 

 Cryptogamists. One of the earliest studies of Mr. E. Brown was 

 Schmidel's Icones, a work which anticipates many modem observations, 

 as the spiral structure of the threads in Trichia, and the motion of the 

 Spermatozoids in Jungermannia, and one of the best memoirs on the 

 development of the embryo in vegetables, is that of Tulasne. 



