October 23, 1896.] 



SCIENCE. 



605 



19. 'Some Abnormal Chick Embryos,' 

 was a paper by C. W. Hargitt, reviewing 

 some of the more striking facts of teratology, 

 of the time. Also noticing the remarkable 

 advances and significance of modern em- 

 bryology, and the apparent climax as shown 

 in the striking experiments of Driesch, 

 Eoux, "Wilson and others, shows the 

 probably similar character of experiments 

 of Dareste, Metrophanow, and others on 

 the embryology of the chick. 



The paper next dealt with special examples 

 of abnormal chick embryos which have 

 <3ome under the writer's observations quite 

 recently, several specimens of which were 

 exhibited. 



Various phases of irregularity were noted, 

 such as imperfectly developed embryos ; in 

 some only the head-fold ; in others hardly 

 beyond the primitive groove ; in some other 

 embryos degeneration of the whole blasto- 

 derm, even after considerably advanced 

 stages. Several cases of double and triple 

 embryos were noted. 



20. ' On a peculiar Fusion of the Gill-fila- 

 ments in certain Lamellibranchs,' by Ed- 

 ward L. Eice. 



In many folded types of lamellibranch 

 gills the examination of serial sections per- 

 pendicular to the filaments shows a large 

 number of filaments in the upper portion of 

 the gill, which gradually meet and fuse to 

 a relatively small number as the free mar- 

 gin is approached. Thus in Cardium edule 

 a reduction of 23 filaments to 6 was noted. 



The fusion is usually almost exclusively 

 limited to a narrow band in the near vicin- 

 ity of the free borders of the gill, where the 

 folding of the lamellae is necessarily much 

 reduced. Another zone of fusion may be 

 noted, in cases where the outer gill is pro- 

 duced to form a dorsal appendage, at the 

 transition from the gill proper to the ap- 

 pendage. Here again the fusion is correl- 

 ated with a reduction in the folding. 



Is this phenomenon really a fusion or a 



branching of the original filaments ? At the 

 free border of the gill the filaments of one" 

 lamella go over without interruption into 

 those of the other, and the number in the 

 two lamellae must in either case be equal. 

 In the ' zone of fusion ' the number becomes 

 very unequal. Higher in the gill, where 

 the maximum number is reached, the two 

 lamellae contain equal numbers of filaments, 

 showing conclusively that the maximum is 

 the original number. 



This fusion was observed only in distinc- 

 tively lamellar gills in which the folding is 

 developed. It is most conspicuous in Car- 

 dium, Batissa, Psammohia, Chaina, Soleno- 

 curtus and Donax serra; less developed in 

 Cyprina (strong on the transition line of 

 gill proper and appendage) and Venus; 

 very slightly developed in Solen, Mya, and 

 Donax politus. Though fusion was observed 

 in Cytherea, Donax trunculus, Ostrea, and 

 Thrada, nor in the outer gill of Cardium and 

 JPsammobia. 



The fusion seems to have little systematic 

 value, but to be mechanically correlated 

 with the folding and the crushing due to 

 the inelastic gill margin with an increasing 

 number of filaments. The upper part of 

 the gill of Cardium, if flattened, would 

 measure some seven times the length of the 

 free margin. 



Apparently this fusion has not been noted 

 in the literature, unless figures showing an 

 unequal number of filaments in the two 

 lamellae, within onefold, point in this direc- 

 tion, e. g., Cardium (van Haren), lAma 

 (Pelseneer), Donax truncidus (Sluiter), 

 Ostrea (Kellogg). 



21 . 'Experiments Upon Regeneration and 

 Heteromorphosis,' by Chas. W. Hargitt. 

 This paper reviewed a series of experiments 

 carried on at the Marine Biological Station 

 during the present summer upon regenera- 

 tion among the Hydromedusae. The ex- 

 periments of earlier investigators upon 

 hydroids were repeated among various fam- 



