334 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



again and again subdivide. If these are noted and it is observed tliat they are 

 engorged, giving them the appearance of a simple series of much-branched great 

 veins filled with creamy white contents, it may be certainly presumed that your 

 specimen is mature and that spawn may be readily pressed from it. 



The operation of pressing the spawn out of the ducts requires care. The side of 

 the end of the pipette may be used, being careful not to crush or break open the 

 ducts as you gently and firmly stroke the pi])ette flatwise over the side of the 

 visceral mass backward from the hinge toward the heart space and over the great 

 duct at the border of the latter diagonally downward and backward to the opening 

 of the reproductive organ. If this has been properly done it will be found that the 

 generative products are being 'iiushed forward by'the pipette through the ducts, as 

 the pressure will be seen to distend the latter, the contents of the branches flowing 

 into the larger and larger trunks until they are forced outward through the main 

 duct and opening below the great adductor, where they will pour out in a stream 

 one-sixteenth of an inch or more in diameter if the products are perfectly ripe. The 

 sexes may be discriminated as described at the outset, and it is well to first find a 

 male by the method already given and proceed to express the milt as described 

 above into, say, a gill of sea water, adding pipetteful after pipetteful until it acquires 

 a milky or opalescent white color. As the milt or eggs are i>ressed out of the open- 

 ing of the ducts, they are to be sucked up by the pipette and dropped into the water, 

 the mixture of milt being first prepared, to which the eggs may be added as they 

 are expressed from the females. The judgment of the operator is to be used in mix- 

 ing the liquids ; in practice I find that one male Avill supply enough milt to fertilize 

 the eggs obtained from three or four females, and it does not matter if the operation 

 takes from twenty to thirty minutes' time, as the male fluid, which it is best to 

 prepare first, will retain its vitality for that period. 



It is always desirable to be as careful as possible not to get fragments of other 

 tissues mixed with the eggs and milt, and the admixture of dirt of any kind is to be 

 avoided. To separate any such fragments nicely, I find a small strainer of coarse 

 bolting or cheese cloth to be very convenient. 



In the foregoing description we have described the method of obtaining the spawn 

 only from the side of the animal exposed in opening the shell. A little experience 

 will enable one to lift up the head end of the animal and throw it back over the great 

 adductor muscle, expose the opening of the reproductive organ on the left side, 

 or whatever the case may be, and also express the spawn from that side, thus as 

 eff'ectnally obtaining all of the ripe eggs or milt as is possible in the process of 

 taking the same from fishes. 



It is remarkable to note the success attending this method, since almost every egg 

 is perfect and uninjured, the percentage of ova, which are impregnated, is muchlarger 

 than by the old method, reaching, I should say, quite 90 per cent of all that are taken 

 when the products are perfectly ripe. It is also found that the products are not so 

 readily removed by my process if they are not perfectly mature, which is also to 

 a certain extent a safeguard against jioor or immature spawn. In the course of 

 an hour after the products of the two sexes have been mingled together it will 

 be found that nearly every egg has assumed a globular form, has extruded a polar 

 cell, lost the distinct germinative vesicle and spot in the center, and begun to develop. 



It is noteworthy that our practice as herein described has completely vindicated 

 the statement made by the distinguished French anatomist and embryologist, M. 

 Lacaze-Duthiers, that there is biit a single generative opening on each side of the 

 visceral mass of the oyster, and that, as we have«tated, it is found to open just below 

 the great adductor muscle. 



We have also discovered, since the foregoing was written, that the use of an 

 excessive amount of milt is of no advantage. The water in which the eggs are to be 

 impregnated only requires to be rendered slightly milky ; a very few drops of good 

 milt is sufficient to make the impregnation a success. Too much milt causes the eggs 



