374 SUMMARY OF CURRENT RESEARCHES RELATING TO 



perihsemal spaces are ciliated does not seem to have been previously 

 ascertained. The absence of ciliation from the lining of the peri branchial 

 spaces is noteworthy. 



The relation of larval to adult ciliation is discussed. While it is 

 true that the larval ciliation passes into that of the adult, the changes 

 in shape and structure which take place at metamorphosis are so pro- 

 found that in the end only a few details of correspondence between the 

 two systems can be made out. 



In the case of Porania pulvillus there is a definite arrangement for 

 ciliary feeding, and experiments show that this kind of feeding actually 

 takes place. As regards Astropecten it is also shown, so far, that the 

 arrangement of the actinal and abactinal cilia makes ciliary feeding 

 possible. In Solaster papposus ciliary feeding probably takes place, but 

 in an entirely different degree. The other starfishes examined gave 

 negative results. It may be that the hypothetical fixed ancestor fed by 

 ciliary activity during the time when it was becoming, and for some 

 time after it had become, an Asterid. 



Mechanism of Fertilization in Arbacia.* — Frank E,. Lillie finds 

 that unfertilized ova in sea-water produce large quantities of a 

 substance which he calls fertilizin. This is conceived of as react- 

 ing with the sperm (its " spermophile " side-chain) and with the 

 egg (its " ovophile " side-chain). The secretion begins presumably 

 in the ova, with breaking of the germinal vesicle. Although the 

 jelly is saturated with it, and liberates it by solution in the sea-water, 

 eggs without jelly continue to secrete it for three days, at least, during 

 repeated washings, or as long as they remain alive. The spermatozoa 

 of Arbacia possess extreme avidity for the fertilizin, and bind it in 

 definite amounts. In the case of fresh active sperm the binding is 

 evidenced by reversible agglutination of the spermatozoa. But a stale 

 sperm suspension may also bind it, although the agglutination does not 

 take place, except in high concentration. The fertilizin of Arbacia 

 eggs does not combine with Nereis sperm. 



A substance, named anti-fertilizin, may be extracted from Arbacia 

 eggs, by breaking them up or by extracting them in distilled water, 

 which has the property of combining with the spermophile group of 

 the fertilizin. It is present in sufficient amount to neutralize all the 

 fertilizin contained in the eggs, excluding the jelly. When the fertilizin 

 is extracted from the eggs by repeated washings, they are no longer 

 capable of fertilization. Fertilized eggs produce no more fertilizin ; 

 that present at the moment of fertilization is neutralized by anti- 

 fertilizin. Eggs with membranes formed by butyric acid become in- 

 capable of fertilization.; and they contain no free fertilizin. 



The blood of male and female sea-urchins contains a varying 

 amount of a substance which inhibits fertilization without exerting any 

 injurious effect upon either the sperm or the ova. This substance is 

 probably more abundant in the blood of mature individuals than in 

 others. The inhibitor does not act by blocking the combination of the 



* Journ. Exper. Zool., xvi. (1914) pp. 523-90 (1 fig.). 



