Euphausiidæ. 15 



presented by the cortical substance. It is highly probable 

 that this substance, on coming in contact with the water, 

 swells up, and thereby forces the central mass into the cup- 

 shaped pieces, and from these through the narrow ducts 

 which open on the surface of the sphere. The terms here 

 proposed of spermatocyst for the inner body of these 

 spheres, and ejaculatory ducts for the cords connecting 

 this body with the external envelope, may thus be justified. 

 It must, however, be noted, that as yet I have not seen these 

 spheres escaping from the body of male Euphausiidæ, nor 

 have I directly witnessed the penetration of the supposed 

 spermatic matter through the external envelope of the 

 oosphères, though, as above stated, an apparently very 

 similar matter has in some cases been found inside this en- 

 velope. It is only when these observations have been made, 

 that complete evidence can be obtained as to the correctness 

 of the extraordinary explanation of the propagating-spheres here 

 given. At present this explanation has merely the character 

 of an hypothesis, and it is, indeed, only after long hesitation 

 that I have ventured to set forth my suggestions about 

 this matter, at they seem to stand in contradiction to all 

 that is hitherto known. It has, however, been quite im- 

 possible for me to find any other mode of explaining the 

 above-described remarkable structural features of the spheres. 

 As above stated, both the oosphères and spermato- 

 spheres are kept freely suspended in the water, and ap- 

 parently occur in dense crowds; but their specific weight 

 is so very exactly adjusted to a fixed degree of saltness of the 

 water, that the slightest change in this respect will cause them 

 to sink down to the stratum that exhibits the right composi- 

 tion. At Drøbak, more frequently the upper strata of the 

 sea have a less degree of saltness than the deeper, and for 



