98 E. E. JUST. 



(a) Both eggs and spermatozoa are injured by the sea-water. 



(b) The sperm alone are injured by the sea-water. 



(c) The eggs alone are injured by the sea-water. 



The failure of the eggs to go beyond maturation may be due 

 to the injurious action of the sea-water on both eggs and sperm 

 alike. It would seem reasonable to assume that for internal 

 insemination both cells need the perivisceral fluids. It might be 

 difficult to conceive how this adaptation in Platynereis could have 

 taken place acting on one only of the sex elements. As both eggs 

 and spermatozoa are protected by body fluids in normal insem- 

 ination, so both are exposed to the lethal action of sea-water. 

 Embryologists are all careful when inseminating eggs of forms in 

 which insemination normally taken place in the sea not to con- 

 taminate the dishes containing ova with the animal's tissues or 

 fluids. Lillie ('13&, '14) has shown why this is essential. I have, 

 however, repeatedly with success fertilized Nereis eggs dry (see 

 Just, '15&) doubtless because the body fluid of Nereis is practically 

 negligible. And the case of Platynereis is similar to that of 

 Nereis; in this smaller worm there is no more fluid; the female 

 is a mere locomotor ovary, although the male does have a small 

 amount of fluid and a great number of corpuscles. 



The second possibility is that the sperm alone are injured by 

 the sea-water. Injury to the sperm through transference from 

 the male's body fluid to sea-water, however, cannot be due to 

 difference in osmotic pressure. For as Fredericq has shown, and 

 Garrey since for the Woods Hole region, the osmotic pressure of 

 invertebrate body fluids is about the same as that of sea-water. 

 Moreover, Platynereis sperm in sea-water as far as I could de- 

 termine exhibit none of the effects experimentally produced by 

 Koltzoff on various sperm cells including those of Nereis {dumer- 

 ilii?) through treatment by various salt solutions or those con- 

 ditions described by de Meyer with hypotonic and hypertonic 

 solutions. In some other way, then, the sperm must be assumed to 

 be weakened but still capable of partially fertilizing the egg as the 

 Hertwigs, Gemmil, Budington, Dungay, etc., have shown. And 

 indeed my Platynereis slides of sea-water inseminated eggs show 

 similarities to the figures by Lillie of the penetration of injured 

 sperm in Nereis; in Platynereis, however, the germ nuclei develop 



