770 



SCIENCE 



[N.B. Vol. XXX. No. 778 



F. majalis embryos were dealt with by the 

 writer as physiological conditions resulting 

 from an incompatibility of the germinal ma- 

 terials involved, and furnished the basis for 

 the discussion of a number of general ques- 

 tions. It was, then, somewhat of a shock to 

 learn through the kindness of Dr. H. D. 

 Senior, of the Syracuse University Medical 

 School, that the well-known ichthyologist, 

 John A. Ryder, had in 1885 described Fundu- 

 lus majalis as a viviparous species. If Ryder's 

 statement were correct it would be necessary 

 completely to revise all statements made by 

 the present writer that were based on the as- 

 sumption that the species in question is 

 strictly oviparous. The failure to hatch, for 

 example, might be due to abnormal environ- 

 ment. 



In the paper referred to" Ryder, after deal- 

 ing with certain well-authenticated cases of 

 viviparity among the Poecilliidse, describes in 

 a final paragraph (p. 155), under the heading 

 " The Viviparity of Fundulus" another type 

 of viviparous embryo, differing from 0am- 

 husia in having a distinct zona. The vitelline 

 circulation is described and several points of 

 similarity between Fundulus and Gamhusia 

 are noted. 



On Plate XL, figs. 29 and 30, are pictured 

 two rather advanced embryos of Fundulus 

 majalis, described in the legend as having been 

 " forced from the ovary by pressing the ab- 

 domen of the living fish." These figures bear 

 a general resemblance to the corresponding 

 stages of the F. majalis embryos studied by the 

 writer, but might readily represent those of 

 some other species. The thick gelatinous en- 

 velope characteristic of the extruded eggs of 

 F. majalis is omitted in the figures. 



During the past summer the opportunity 

 was offered for thoroughly testing the ques- 

 tion of viviparity in this species, and the re- 

 sults of the test force the conviction that 

 Fundulus majalis, as it occurs at Woods Hole, 

 Mass., is strictly oviparous and that the con- 

 clusions expressed by the writer in the paper 



^ " On the Development of Osseous Fishes," Pro- 

 ceedings of the United States National Museum, 

 Vol. VIII., No. 9. 



on Fundulus hybrids are founded on no mis- 

 conception regarding the normal mode of 

 gestation of the F. majalis embryos. 



The following are the considerations that 

 have forced this conviction : 



1. Literally thousands of females of this 

 species have been stripped by the writer and 

 by many other students and investigators dur- 

 ing the past decade, and no one has ever re- 

 ported the extrusion of an egg containing an 

 embryo. 



2. This summer many females were opened 

 at all stages of the breeding season. In no 

 case were embryos found. 



3. The number of eggs extruded at one 

 time by a single female may run from 200 to 

 800. This number is far in excess of that 

 which could possibly develop within the 

 mother. It is well known, moreover, that vivip- 

 arous species, whether with ovarian or oral 

 gestation, have small numbers of eggs, usually 

 not over 25 to 50. 



4. The eggs are provided with a thick, 

 somewhat fibrous, gelatinous coat, that causes 

 them to adhere, after extrusion, to objects on 

 the bottom. The function of such an envelope 

 could scarcely be conjectured on the assump- 

 tion that the species is viviparous. 



5. A study of the spawning behavior of F. 

 majalis has shown that, at least in captivity, 

 the eggs are extruded during the spawning act 

 and are fertilized externally by one or by sev- 

 eral males. 



6. The anal fin, which, in truly viviparous 

 species like Gamhusia, is modified into a stiff, 

 pointed intromittent organ, is, in F. majalis, 

 soft, blunt and in no way adapted for intro- 

 mission. 



7. Several masses of normally developing F. 

 majalis eggs were found in the sand at low 

 tide, closely associated with the eggs of 

 Limulus. These eggs were identified as be- 

 longing to the species mentioned by several 

 investigators at the Woods Hole laboratories. 



There appears, then, to be a marked discrep- 

 ancy between Ryder's statement and the facts 

 here detailed. No satisfactory explanation of 

 so wide a divergence of statement offers itself 

 at the present time. It might be suggested, 



