308 EMBRYONIC DEVELOPMENT 



On the fifth of October, 1850, this memoir was read before the Boston Society of 

 Natural History,* and referred to the publishing committee, which reported in favor 

 of publication in its Journal whenever the funds of the Society could meet the ex- 

 penses required by the illustrations. 



At the suggestion of several of my New England friends, T withdrew the memoir 

 upon my leaving the North, hoping to find a speedier way of bringing it before the 

 public. But circumstances out of my control have occasioned a delay of three years, 

 during which period several works of embryology have passed through the press, which 

 although not treating of the same special subject, would have induced me to modify 

 gome of the paragraphs of my original memoir, had I not desired to preserve the form 

 in which it was originally written. 



A few paragraphs, however, have been added to the chapter on the fecundation, and 

 to the conclusion, in which I have felt it my duty to refute an assertion since made 

 against the views I hold in regard to the systematic position of Planaria. 



C.G. 



Washington, Nov. 1, 1853. 



I. THE EGG BEFORE IT IS LAID. 



I have seen the egg when it was but a simple cell, which the most practiced eye 

 could not have distinguished from the constituent cells of the organic tissues, had its 

 situation and its further development not been a subsequent warrant of its true nature. 

 This first observation was made in the fall of 1848. The eggs, at that season were 

 undoubtedly primordial cells, formed according to the process to which I have called 

 attention elsewhere.f These cells now, were to take a predetermined development, 

 a given direction ; in other words, lead a life independent of the life of the maternal 

 body, endowed with a circle of activity of their own. From that time they become 

 the initial centre of as many individuals, although still connected with the original 

 matrix. 



Indeed, during the ensuing winter, these primordial cells had already acquired 

 such a development, that any one, familiar with the subject, could recognize an egg 

 at the very first glance. Their size was considerably increased, and the germinative 

 vesicle and germi native spot, being now present, there was no possibility of being 

 mislead in regard to them, even if the eggs, compared with the size of the organic 

 cells, had not answered all objections. 



Besides the germinative vesicle and the germinative spot, the nature of the con- 



* Proc. Bost. Soc. Nat. Hist. iii. 1850, 348. 

 "fAmer. Jour, of Sc. and Arts, 2J series, vol. ix. 1850. 



