IF, 

 *y - 



56 



fouud. There are tliree bottles in tlie collectiou, oiie of wliich contains the spawn 

 of the comrnon Cottus and is labelled: 



D. 5 — 1 — 95. Marens Rev at Frederikshavn (northern Kattegat), spawn, coUected by 

 L. Kolderup Rosenvinge. 



The other three bottles contain the spawn of the long-spined Cottus; they 

 are labelled: 



D. 15 — 5 — 90. Holbæk Fjord (north coast of Sealland). Sjmwn laid on a set-net. 



D. 22 — 5 — 90. Holbæk Fjord. Spmim from a set-net (probablv a portion of the one foiind 

 on the 15th) witli whoUy or almost whoUy escaped young. 



Middle of April — 91. Føns Skov (Little Belt). Spawn fonnd on beacli. 



As a result of these observations we may say concerning the spawniug 

 period of the two species of Cottus in the Danish waters, that the common Cottus 

 spawns in December — January and the long-spined Cottus in April — il/«//. 



In consequence of the difference in the spawning time of tlie two species, 

 the pelagic young also appear at different periods of the year. 



The pelagic young of the common Cottus occur already in January. 



In 1892 the Director found pelagic Cottus young in Fænø Sound in Jan- 

 uary — May. There can be doubt that the young taken in January at any rate 

 belonged exclusively to the common Cottns. 



In 1902 a uumber of the young of the common Cottus were sent from 

 Nyborg (Great Belt) to Copenhagen in January. They were taken in the well of 

 "Stationen'' and were small, all with yolksac attaciaed. When "Stationen" was 

 moved to Fænø and lay there from March 5th to May 22nd, the occurrence in 

 qnantities of the young of the common Cottus could be followed from day to day. 

 These young were most abundaut in March; on March 2ord 169 young of the 

 common Cottus were taken in one of the "bobinet" nets; the net had been hang- 

 iug in the current for 1'/, hours. Even in the beginning of April the young of 

 the common Cottus were present in most of the catches of pelagic young. At the 

 end of April they became scarcer and were quite absent in May, in which month 

 only one pelagic young of the common Cottus was taken in Fænø Sound, namely 

 on May 7th. 



In 1903 we took the pelagic young of the common Cottus in the months 

 February — May (see Tab. 3 A), but in May not later than the Ist, when we took 

 two in the young-fish trawl in the western Baltic at Ærø. 



During tlie February cruise of the »Poseidon« in 1903 Ehrenbaum and 

 Strodtmann found the pelagic young of the common Cottus in the western and 

 the true Baltic. They found none in these waters in May. 



When A. C. Johansen began his spring cruise in 1904 (see Tab. 1, North 

 Sea, Skager Rak and Kattegat, February — March), the pelagic young of the common 

 Cottus were common, but they were not evenly distributed over these regions. 

 Johansen found many in the Kattegat on Fehruary 16th but none in the Skager 

 Rak on the 17th. The result of some hauls in the North Sea with the young-tish 

 trawl on Februarj^ 26th was a single pelagic specimen ot the common Cottus. On 

 the return cruise from the North Sea in March Johansen again found no pelagic 

 young of the common Cottus in the Skager Rak, but many in the Kattegat. During 

 our March cruise with the »Sallingsund« in the Great Belt, western and true Baltic 

 (see Tab. 1) we fouud everywhere many pelagic young of the common Cottus. 



