ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 375 



sperm receptors with the fertilizin, for it has no inhibiting effect upon 

 the agglutinating action of the fertilizin. It acts by occupying the 

 ovophile group of the fertilizin, thus preventing action of the latter 

 upon the egg by union with egg-receptors. This conclusion is de- 

 monstrated by the fact that the inhibitor may be entirely neutralized 

 by a sufficient quantity of the agglutinating substance. 



Lillie's general idea is that the formation of the fertilization 

 membrane is due to the activation of an ovogenous substance (fertilizin). 

 Following insemination, any excess of fertilizin is bound, or neutralized, 

 by another ovogenous substance (anti-fertilizin), and polyspermy is 

 thereby prevented. The intimate nature of the reactions that occur 

 remains unknown, but as a mode of formulation Lillie expresses them, 

 in terms of Ehrlich's immunity hypothesis, as definite lock-and-key 

 chemical combinations. 



Ccelentera. 



Development of Mesenteries in Anthozoa.* — Thomas Clachai 

 Brown comes to the following conclusions as the result of his studies. 



All Anthozoa, Palaeozoic, Mesozoic, and Modern are derived from 

 one common stem-form in which the zooids were bilaterally symmetrical 

 and probably had eight mesenteries. 



One branch from this common stem, arising early in the Ordovician, 

 leads up to the modern Alcyonaria (Octocoralla). To this grand sub- 

 division probably belong all such genera as Golumnaria, Favosites. 

 Nt/ioJites, Syringopora, etc., which are either without septa, or have 

 apparent septa (pseudosepta) or septal spines which bear no direct 

 relation to the soft parts of the zooid either in number or in position. 



Another branch from this common stem, likewise arising early in 

 the Ordovician, embraces the typical tetramerous corals of the Palaeo- 

 zoic — the Rugosa, having eight primary mesenteries and four primary 

 septa, with secondary septa inserted in the four primary exocceles in a 

 unilateral pinnate manner, and with tertiary septa inserted late in life 

 in the secondary exocceles. This branch of the Zoantharia became 

 extinct, in North America at least, at the close of the Palaeozoic. 



Another branch from the common stem gave rise to the Mesozoic 

 and later Zoantharians — Actinians, Seleractinians, Zoanthids, and Ceri- 

 anthids. All of these pass through an eight-mesentery (Edwardsian) 

 stage in their development, but the great majority of them acquire a 

 later secondary radial symmetry. The particular mode of arriving at 

 this six-fold symmetry varies greatly in the different subgroups. 



Gonophores of TubularidaB.t, — Hjalmar Broch finds that the gono- 

 phores of Tubularids show a very interesting series, which corroborates 

 the interpretation of the sessile gonophore as a reduced M'dusoid. In 

 the female gonophores of Tubularia indivisa, the radial canals are seen 

 in the earlier stages and afterwards disappear. This must mean that 

 the gonophores of ancestral forms had well-developed radial canals. 



* Amer. Journ. Sci., xsxix. (1915) pp. 535-42 (11 figs.). 



t K. Norske Vidensk. Selsk. Skrifter, 1914, No. 2, pp. 1-17 (4 pis. and 1 fig.). 



2 1. 2 



