December 9, 1921] 



SCIENCE 



579 



plutei. Of those which had stood for more than 

 57 hours, however, only a very few reached the 

 four-cell stage, no further development taking 

 place. 



The eggs taken out from inside the shell, on 

 the other hand, showed invariably a high fer- 

 tilizability, even when much of the " perivis- 

 ceral fluid " (" blood ") had been mixed in 

 water and no washing followed. After more 

 than 28 hours' standing in room temperature, 

 and without subsequent washing, they could be 

 fertilized and they developed into plutei, while 

 among those which had stood for more than 

 47 hours very few could segment and reach the 

 gastrula stage.^ 



The substance, which inhibits the fertiliza- 

 tion and which probably can, to some extent, 

 thus prolong the life of the unfertilized egg, 

 has been found to come from the surface of the 

 body of the sea-urchin. This I may call " der- 

 mal secretion." If a sea-urchin is opened and 

 inverted over a dry dish for a while some dull 

 yellowish fluid collects in the dish. When the 

 eggs taken out from inside the shell were in- 

 seminated in this " dermal secretion," no mat- 

 ter whether the latter had been obtained from 

 male or female animals, fertilization was found 

 inhibited in varying degrees according to the 

 concentration of the fluid. The dermal secre- 

 tion, when present in a 5 per cent, concentra- 

 tion in sea-water, was found sufficient to in- 

 hibit all the eggs from fertilization. In 2.5 per 

 cent, solution about 10 per cent, of the eggs 

 fertilized, and in 1 per cent, solution about 50 

 per cent, of the eggs developed. When present 

 in less than 0.5 per cent, concentration prac- 

 tically every egg could be fertilized. 



If, however, the eggs were treated with a 

 strong solution of this substance after fertili- 

 zation no injurious effect was found on the 

 early development as late as the pluteous stage. 

 The activity of the spermatozoa also does not 

 seem to change in this fluid. 



The dermal secretion thus obtained from 

 Ariacia has some inhibitory action also on the 



3 As to the longevity of the unfertilized egg of 

 Arhama see A. J. Goldfarb, Biol. Bull., XXXIV., 

 6, 1918, pp. 393-5; and E. N. Harvey, Biol. Bull, 

 XXVII., 5, 1914, p. 238. 



eggs of the sand-dollar, EchinaracJinius parma, 

 though in a lower degree. In a 15 per cent, 

 solution of this fluid in sea-water none of the 

 sand-dollar eggs were found fertilized, in a 10 

 per cent, solution about 1 per cent, of the eggs 

 developed, and in a 5 per cent, solution about 

 20 per cent, of the eggs developed. 



Through the kindness of Dr. H. C. van der 

 Heyde the substance in question was shown to 

 contain uric acid. From lack of sufficient time 

 I was unable to see if uric acid alone dissolved 

 in sea-water would exhibit the same action upon 

 the egg as the dermal secretion does. 



The same substance could also be obtained in 

 some other ways: for example, by placing an 

 intact sea-urchin on a dish for a while, no mat- 

 ter which side down, after being washed with 

 fresh water, or by irritating the animal with the 

 sharp point of a glass needle instead of treating 

 with fresh water. On the other hand, sea-water 

 in which some scraped pieces of skin, tube-feet, 

 spines, etc., had been soaked for some time 

 showed very little inhibitory effect upon the 

 fertilizability of the egg. 



According to Lillie* the perivisceral fluid of 

 Arhacia inhibits the fertilizability of the egg, 

 whereas the dermal secretion protects the egg 

 from the inhibitory action of the former. I 

 have found that the perivisceral fluid had very 

 weak inhibitory action upon the fertilizability 

 of the egg; thus in a 50 per cent, solution of 

 the same in sea-water about 5 per cent, of the 

 eggs fertilized, and even in a 75 per cent, solu- 

 tion about 1 per cent, of the eggs could be fer- 

 tilized. Although it may seem quite contrary 

 to Lillie's conclusions, my results rather con- 

 flrm his view that the inhibitory action of the 

 perivisceral fluid increases during the period 

 when sexual elements are ripe. Lillie's experi- 

 ments were mostly made in July, when the 

 gonads of Arhacia are quite active, while the 

 breeding season comes nearly to an end early 

 in September, when my material was obtained. 



It is well known that among Echinoderms, 

 especially Holothurians, there are several 

 species in which the eggs are fertilized and 

 develop inside the mother's body-cavity. In 

 such cases it seems highly improbable that a 



4 Jour. Exper. Zool., XVX., 4, 1914, pp. 570-7. 



