334 KOREN AND DANIELSSEN ON THE 



mode of development appears to us to be of great physiological 

 importance and will assuredly be confirmed by further obser- 

 vations. With regard to the number of ova which are grouped 

 together for the formation of a single embryo, there is consider- 

 able variation, and it seemed to us to be the greater, the greater 

 the number of the ova in the same capsule. In the mean, each 

 capsule contains from six to sixteen embryos ; however, we have 

 found as many as thirty- six. The more ova there are in a capsule, 

 the more of them there are in each mass, whence we sometimes 

 meet with embryos which have at their first appearance a very 

 considerable size, attaining in fact as much as 1^ millimetre. 

 The number of ova united into one embryo varies from 40 to 

 60 ; we have often, however, met with as many as about 130. 



Gray long since observed*, that a capsule enclosing more than 

 a hundred ova yielded only four or five embryos. The English 

 physiologist explains this fact by the law of atrophy, that is to 

 say, by supposing that the great increase of some ova hinders the 

 development and ultimately effects the destruction of the others. 

 It remains to be seen whether Gray deceived himself, or whether 

 it is we who have fallen into error. We believe that he was on 

 the right track, but did not attain to the exact truth. 



After having seen that the ova group themselves together, to 

 form the embryo, and become coated by a delicate and trans- 

 parent pellicle, we now proceed to explain the manner in which 

 the various organs make their appearance. The first step is 

 the exudation of a clear, finely granular substance over the 

 surface of the ova, which then begin to appear more trans- 

 parent. We perceive in this mass, a multitude of cells which 

 continually multiply ; it then takes on a distinct form and be- 

 comes bilobed (fig. 4c). These lobes are gradually provided 

 with cilia, and the first movements are exhibited. The foot, 

 which is formed in a corresponding manner, appears as an 

 eminence, distinct from the remainder of the body, and pre- 

 senting cilia ; the embryo then turns upon itself in an extremely 

 slow manner (fig. 5e). Scattered cirrhif now make their ap- 

 * Annales des Sciences Naturelles, 2 Ser. torn. vii. p. 375. 

 f Sars drew a distinction between the long cirrhi which are found on the 

 lobes and the cilia, and proposes to call them natatory hairs (Svremmehoar). 

 Subsequently many authors have called them cirrhi, retaining the name of 

 cilia for the very short, fine hairs. 



