IO6 BASH FORD DEAN. 



clearly has nothing to do ? Can it, for example, start an egg on 

 its course of development and then provide it with a capsule 

 whose special structures shall "foresee" accurately what the 

 young is to become ? Can it form a capsule which shall have 

 the power, in spite of its lifeless substance, to develop as the en- 

 closed egg develops, so that at each period it can best serve the 

 corresponding stage of the embryo's growth ? Such instances, if 

 they can be found, are evidently of value in the examination of 

 the complex problems of heredity. 



The following notes are given since they appear to illustrate 

 an extreme case in point : and since they also indicate that some- 

 what similar " purposeful " conditions may be demonstrated in 

 the secondary embryonic membranes of other forms, i. c., that 

 these structures may be found the better adapted to the future 

 grade of development of an embryo than has hitherto been 

 suggested. 



In examining the shark-like fish, Chim<zra{C. colliei], the egg- 

 capsule was found to be specialized, i. e., adapted for the embryo 

 at a late stage of development, rather than for the egg, in the 

 following characters (Cf. figures in BIOL. BULLETIN, 1903, Vol. 

 IV., pp. 271, 272): 



I. /;/ Size. The capsule is not fitted to the egg ; in fact, the 

 outline of the egg is squeezed into a long ellipse, in order that it 

 may be contained in the case, for if the case be opened and the 

 tension relaxed the egg regains its circular outline, and the capsule 

 with its appendage is then much (about nine times) longer than 

 the egg. The great size of the capsule (longer in proportion to 

 the adult body than that of a single egg of any known animal) 

 is in evident adjustment to the advanced development of the 

 young fish at the time it is cast upon its own resources. In 

 point of fact it is then well grown about one fifth the length 

 of the adult --and by this time it has entirely lost its yolk and 

 resembles the parent in remarkable detail in axial and appen- 

 dicular skeleton, in fins, viscera, in dermal, even in secondary 

 sexual characters, c. g., clasping organs of male. 



II. In Shape.- -The capsule as laid down in the oviduct is 

 divided into special regions destined to contain the snout, trunk 

 and tail of the young (at time of hatching). In earlier stages 



