f25] EGGS OF THE PLAICE, FLOUNDER, AND COD. 451 



The medusae are probably a dangerous enemy to the eggs. Earle 

 states : 



"One day I i)laced a medusa or medusoid, measuring only 1^ inch in 

 diameter, in a trough containing eggs; and in less than five minutes it 

 had gotten 70 eggs in its tentacles, which weighed them down to such 

 a degree as to cause them to be torn o£f the medusa, as it floated through 

 the water." 



The wording of this statement does not prove that the medusce actu- 

 ally eat and digest fish eggs, but I have not the slightest doubt that they 

 do this, as, according to Sars's observations, which are confirmed by 

 mine, they even take young fish. It is only the medusce proper, how- 

 ever, and among these only the Medusa aurita and Cyanea capillata^ 

 which can come into consideration, as far as the Baltic is concerned. 

 In 1882, the Cyanea was very numerous in the Bay of Kiel, but in March 

 they were still so small that they could not prove dangerous to the 

 eggs. The Medusa aiirita, so far as I know, makes its appearance later 

 in the season. In 1883, both these kinds were so scarce, that I only met 

 with 3 or 4, and during that year at least they cannot possibly have 

 destroyed many eggs. 



On the 14th of May I made the somewhat unexpected observation 

 that the small Sarsia tuhulosa, measuring only IJ centimeter, eats fish 

 eggs. I had placed a small number of eggs with broken yolks, meas- 

 uring on an average 1.2 millimeters, in a glass vessel into which a large 

 sarsia had accidentally found its way. When later I took out the eggs 

 for the purpose of examining them several were missing, and the stom- 

 ach part of the sarsice was swelled ou^ considerably. In dissecting the 

 sarsia, I found an egg in the process of decomposition, the shell being 

 still well preserved. It, therefore, seems highly probable that, also in 

 the open sea, the sarsice will seize and swallow eggs. I have, of course, 

 not been able to make direct observations on this subject. For the 

 present I do not, therefore, know whether the sarsice will swallow the 

 larger eggs of the codfish and plaice, and how large they must be to do 

 this. In March and April the sarsice are generally very small and im- 

 mature, and their sexual organs do not reach perfection till May. If 

 it should be proved that young sarsice can swallow eggs, it may be pre- 

 sumed that they destroy a very large number of eggs especially in the 

 bays, for here a single haul of tlie net often brings up handfuls of 

 these animals. In the open sea I have not found them so frequently, 

 but here I found the Syncocyne sarsU, so that there can be no doubt as 

 to their occurrence. 



These different facts, and in addition the possibility that the wind 

 drives ashore large quantities of eggs from the surface water, show 

 that the counting of eggs can only give minimum figures as to the 

 number of fish ; but even these would be valuable. 



Provided the water povssesses sufficient gravity, no portion of the sea 

 is better suited for such experiments than the western basin of the 

 Baltic. 



