216 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



with a very faint yellowish tinge, almost completely filling the egg, and 

 leaving only an extremely narrow space between it and the outer cover, 

 filled with a colorless and utterly incongruous mass. The outer cover 

 or skin is tolerably firm and elastic, and consists, as I have couvinced 

 myself by dissecting it, of four different closely -joined layers. One can 

 discover, with the aid of a strong microscope, numerous small oil-bladders 

 of different sizes, and scattered irregularly over the whole surface of 

 the yelk. The egg has another peculiarity, which in the beginning I 

 overlooked, but which, after having had my attention drawn to it, I 

 found invariably in every egg. This is a small dark spot, only discerni- 

 ble through the microscope, which is found in the outer skin, and which 

 is always near that part of the egg that is turned downward. Its loca- 

 tion is not exactly the same in every egg, for sometimes it is quite close 

 to the lower part, and sometimes a little higher up on the side of the 

 egg; but among the many hundreds of eggs which I have examined I 

 did not find a single one where this dark spot was above the lower 

 quarter of the egg's diameter ; nor a siugle one where it occupied exactly 

 the lowest point of the egg. This spot is the so-called micropyle, which 

 answers a two-fold purpose, namely, to allow the spermatozoa to enter 

 the egg, and, also, during the various stages of development, to draw 

 iu water; in other words, it forms the channel of impregnation, and 

 serves as a respiratory organ. Through the most powerful microscope 

 this spot appears as a circular disk of yellow color, surrounded by a 

 somewhat raised edge, and looking as if it were polished. From this 

 spot a narrow channel passes through the skin of the egg, which ends in a 

 funnel-shaped opening. I have not been able to discover any distinct 

 opening iu the above-mentioned round disk. It is certain, therefore, 

 that it is not merely a hole iu the egg, but seems to be of a porous na- 

 ture and to possess a peculiar power of suction. But how can the sper- 

 matozoa get into the egg through this disk ? To the solution of this 

 problem I have devoted special attention by pouring a drop of milt to 

 the eggs, while under the microscope. I have frequently seen the sper- 

 matozoa, as often as they came in contact with this disk, remain hang- 

 ing there, and I could for a long time observe the movements of tae tail 

 outside, but I never could see them enter into the egg, although this is 

 so entirely transparent that one necessarily must have seen them if they 

 had entered the clear space filled with water between the skin and the 

 yolk. The most plausible explanation of this phenomenon seems to be 

 this, that the spermatozoa, which in reality are only cells, after having 

 been for some time in close contact with the micropyle, were ruptured 

 in consequence of the hitter's suction-power, and that their contents 

 only are absorbed by the egg, a view which, so far as I am aware, has 

 never before been expressed. The spermatozoa of the cod-fish are oval, 

 or rather pear-shaped bodies, to whose pointed end the tail is fastened. 

 The milt, like the roe, is of less specific weight than the sea-water, and 

 it therefore floats upon the surface as soon as it is poured out. This 



