NO. 2194. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 31 



1. The eggs are not ripe at the time the spermatozoa are intro- 

 duced into the oviduct, and it requires at least four to six weeks for 

 them to reach maturity. It is hardly possible for an ej^g to be fei"- 

 tilized so long before it is fully developed. 



2. Segmentation does not begin until the eggs pass out into the ex- 

 ternal sacks; consequently if they were fertilized in the copepodid 

 stage they must then lie dormant during the four to six weeks 

 before they could begin to segment — an extremely improbable pro- 

 cedure. 



3. If the spermatozoa swarmed up the rudimentar}-^ oviduct they 

 would go in sufficient numbers to fertilize every egg and leave a 

 considerable surplus. 



We could hardly concede to the spermatozoa that were left after 

 fertilization the ability to pass back down the oviduct, and they 

 would have to remain in the ovary; but an ovary filled with dead 

 spermatozoa, or for that matter with living ones, Avould hardly be 

 a favorable place for egg development. 



4. The fact that no sperm receptacle can be definitely made out 

 in the adult is what would naturally be expected. It has already 

 been stated that the spermatozoa pass out of the spermatophores 

 into the enlarged end of the oviduct when the copepodid female is 

 fertilized. There is never, therefore, any separate sperm receptacle 

 and none ought to be expected in the adult. Again, this enlarged 

 end of the oviduct in a larva only 1 or 2 millimeters in length is of 

 necessity very small, and it could easily persist in the adult and still 

 escape detection. 



In every genus examined there are convolutions in the oviduct, 

 where it is narrowed before passing out of the vulva, that are 

 posterior to the last egg. Any one of these convolutions is large 

 enough to hold several sperm receptacles the size of the one in the 

 copepodid larva, and it Avould seem more reasonable to conclude that 

 one of them serves such a purpose. 



5. But we are not confined wholly to negative evidence. In a 

 young Pennella flosa^ examined by the present author, the ovaries 

 have already migrated from the cephalothorax into the genital seg- 

 ment, although the larva w-as only 18 mm. in length. But at the 

 posterior end of this segment, a short distance inside of the vulva?, 

 there is an enlargement in each oviduct filled with a mass of some- 

 thing that has every appearance of being spermatozon. This speci- 

 men could not be sectioned to complete the proof, but there would 

 seem to be but little doubt that this is the same enlargement into 

 which the spermatozoa were originally introduced, and, if so, they 

 did not pass up into the ovary. 



Consequently we can only conclude that the spermatozoa remain 

 near the vulva, and that each egg is fertilized not in the ovary 



