CAyADIAX FlHHi:RlEH i:.\ I'i:iHTIO\. 191 ',-13 39 



numerous, but the material of these is of a somewhat casual character, being derived 

 from ouly a few stations, where they must, however, have been present iu great num- 

 bers. 



The proportion between ova and young varies greatly; in the case of Ctenolahrus, 

 we have nearly as many larvae as eggs while of Merluccius, on the other hand, only eggs 

 were found. 



Such a table cannot, however, be used without reserve as a means of calculating 

 the percentage hatched for the different species; the period of time required for deve- 

 lopment of the ova will need to be taken into consideration, as also the age of the 

 young when captured. With most species it is true these points are insufficiently 

 known, but in the case of the cod we have knowledge sufficient for a satisfactory dis- 

 cussion of the question despite the difficulties involved in following the development 

 of ova under natural conditions. 



We know, of course, that the destruction of cod eggs and of the early stages of 

 young must be enormous ; were this not so, the sea would soon become over-populated 

 with cod. As to the particular stage of development at which the germ is specially 

 liable to destruction, however, we know, unfortunately, all too little. 



Professor Apstein has, in his work entitled "Die Verbreiting der pelagischen 

 Fischeier und Larven in der Beltsee und den angrenzenden ^leeresteilen," 1908-09, 

 dealt with these questions, and calculated that 72 cod eggs are required to produce one 

 larva. This applies, of course, only to the waters investigated by him, and similarly, 

 here only for a single year. 



THE CAXADIAX WATERS. 



During the actual collection of the material. Dr. Hjort already noticed that there 

 was a very great majority of newly spawned eggs, the later stages of development, and 

 the larvae, being- far more rare. This was especially noticeable on the cruises of the 

 Pnncess. Wishing to go closely into this question, I have, in determining the ova, 

 noted throughout the number of eggs belonging to earlier and later stages; in the 

 smaller samples all the ova were examined, in the case of the larger, only a represent- 

 ative portion was measured off and investigated, the figures thus obtained being then 

 utilized for calculation of values for the whole. 



In order to keep the work within a reasonable scope, distinction has here been 

 made between three stages only; the first being the '' germinative disc" stage, before 

 the formation of the embryo (figs. 1-2), the second from the early pigmented embryo 

 to well-developed pigmentation (figs. 3-4), and the third with pigmentation character- 

 istic of the species (figs. 5-6). These stages correspond to Apstein's figs. 1-0, 10-18 

 and 19-22, from which these text figures have been taken. 



