— 13 — JOES. SCHMIDT 



spawning time," to seek information on tlio conditions wliicii determine where a given 

 species spawns and wiiere it does not spawn. It lias been of special importance tiiat the 

 region investigated by us is so large that it includes both the northern 

 and southern limits of several species, and for all species either the one or other 

 of these, as we have thus been able often to indicate the external factors which mark the 

 limits. With smaller regions with more unifoim hydrographical and bathymétrie conditions 

 the method used here will hardly lead to any result. It requires large and much diversified 

 regions, as has been the case with the present investigations, which therefore have almost 

 a geographical character. 



With regard to the available literature, only for a very few species could it be con- 

 sulted, namely, for those whose pelagic eggs and larvae were sufficiently well known to 

 permit of a certain determination (and they were not many, especially if one only takes 

 account, as I have done, of the absolutely certain). Even the data on the occurrence of 

 ripe specimens can often not be used directly, as the different authors do not always 

 understand the same thing by the term "ripe", especially also when it is not expressly 

 said that ripe females have been examined, as but little often can be concluded from the 

 occurrence of ripe males with regard to the spawning time and place of a species.^ 



5. Explanation of the tables and charts of distribution 



Finally, I may say a few words on the tables over the catches and on the charts of 

 distribution. 



The tables include all the hauls made in the years 1903—06-' in the true Atlantic 

 and English Channel (on the other hand, not in the North Sea, Skager Rak and Kattegat, 

 see p. 3) with Petersen's young-fish trawl. Concerning the hauls made with other apparatus 

 the tables give no information, but occasionally the results are mentioned in the text. 

 Only the fry of the year (0-group) are included in the tables, not the older fish nor the 

 eggs, as the working out of these both on account of the insuffiency of our present know- 

 ledge and the lack of time has not been sufficiently complete for this purpose. At each 

 station the date, position, depth and temperature at the surface and bottom are noted, as 

 also the length of, wire out (see p. 7). The pelagic fry of the gadoids found were measured 

 in millimeters and arranged in various groups according to length. The number of 

 specimens in the various size-groups are then given for each species. 



If the fry were at any time not accurately measured, as a rule because a sample had 

 been wholly or partly lost, the total number only is then given in brackets (see e. g. St. 

 191, 1904, where 50 young fry of G. merlangus not measured occur). 



Each Chart of distribution represents as a rule 2 or 3 species. The black spots always 

 indicate that the fry of the species in question have not been found there. The coloured 

 spots (red, green, blue) show the places where the species were taken, and the coloured 



' JFor information on the temperature and salinity of the waters not investigated in the spawning time 

 of a species, I have referred to the quarterly hydrographical Bulletin published by the International Bureau. 



'^ Thus at Iceland 1 have found males with running milt in the summer time long after the spawning 

 time of the cod was past. (Of. also the discovery of a ripe male eel in tiuite shallow water in Denmark. 

 JoHS Schmidt: Contributions to the life-history of the eel, p. 238, 1906). 



' The tables further contain the results of the investigations carried out in the year 1908 whilst 

 this work was being printed. 



