842 



SCIENCE. 



[N. S. Vol. XXII. No. 573. 



ually fighting. In these daily combats, the 

 smaller suffered considerably, its filamentous 

 appendages and even the ends of its fins being 

 bitten off. Finally it was killed and pre- 

 served as a museum specimen. Its sex was 

 not determined. 



The larger fish, thus left alone, did not seem 

 to miss its companion. It fed voraciously, 

 eating pieces of oyster, bits of shrimp and 

 small fishes alive or dead. In catching its prey 

 it would with closed mouth draw near, and 

 then opening it suddenly (the premaxillaries 

 and lower jaw protruding considerably), would 

 take in its prey with an instantaneous gulp. 

 Frequently, however, Pterophryne would re- 

 main perfectly quiet amid the Sargassum, 

 holding on to the branches with its hand-like 

 pectorals and waiting for the little fishes to 

 come near it. It grew very fat with high 

 feeding and its abdomen became much en- 

 larged, in front of the anus becoming as 

 square as if it had been cut to shape with a 

 knife. Nothing, however, was thought of this 

 save that the fish was getting very fat. 



About noon, on July 25 (after the fish had 

 been in captivity seven weeks), the writer 

 passed through that part of the laboratory 

 where the aquaria were, and found that the 

 Sargassum-fish had laid a large quantity of 

 eggs which, imbedded in jelly, floated at the 

 surface of the water. The eggs, whose number 

 there were no means of computing, together 

 with the enveloping jelly, formed a long string 

 which would have more than filled a pint cup 

 (250 c.c). This jelly had evidently swollen 

 on contact with the water, for the fish, which 

 was only three or three and one half inches 

 long, had only about one third of the volume 

 of the eggs and jelly combined. After the 

 extrusion of the eggs, the size of the fish was 

 noticeably decreased, and the ' fatness ' largely 

 disappeared. 



The eggs were examined alive and, later, 

 sections were made of them. The germinal 

 disk begins to form shortly after the eggs are 

 laid and this fact is noteworthy, in that, ac- 

 cording to Agassiz and Whitman, in pelagic 

 fish eggs this is generally not formed until 

 after fertilization. The formation of the 

 germinal disk, however, proceeds unequally 



rapidly, and, at the end of four and one half 

 hours (at which time the eggs now in my pos- 

 session were killed), had in no egg examined 

 made such a round, clearly marked off, button- 

 shaped disk as all workers have found in the 

 egg of the salmonoids, and as I have figured 

 for the pipefish, Siphostoma floridce. On the 

 contrary, observations on the living egg, con- 

 firmed by the study of sections, show that the 

 germinal disk is partly sunken in a depression 

 in the yolk, half of its thickness being below 

 the general level of the yolk. The germinal 

 disk in the eggs of the Salmonidse is sunken 

 in a depression, in the center of which it forms 

 a mound, touching the yolk only at its base. 

 In Pterophryne, however, the protoplasm en- 

 tirely fills the depression in the yolk (this in 

 eggs four and one half hours old), a phe- 

 nomenon, so far as I know, not before reported 

 for any teleostean egg. 



The protoplasm first exists as a shell of 

 uniform thickness surrounding the yolk, and 

 in the living egg, shortly after it begins to 

 thicken at one pole to form the germinal disk, 

 there may be seen in optical section a clearly 

 defined nucleus. On the contrary, however, 

 I have never been able, either in sections or 

 in the living egg of the pipefish, to find a 

 nucleus in the one-celled stage. Unlike most 

 pelagic eggs, there are no oil drops visible in 

 the living egg of Pterophryne. In sections, 

 some eggs show a small number of minute 

 vacuoles indiscriminately scattered under the 

 germ disk and around the circumference of the 

 yolk; some are devoid of these, and two eggs 

 had two large ones each. These vacuoles were 

 in life presumably filled with oil drops, which 

 have been dissolved out by the alcohol. In 

 the living eggs, no oil drops were ever seen 

 and until the sections had been examined the 

 writer was confident none existed. Indeed, 

 they would seem to be a negligible quantity. 

 The function of the jelly then evidently is to 

 serve as a float to keep the eggs at the sur- 

 face of the water. 



The yolk is colorless and without texture, 

 and, being perfectly homogeneous, is so 

 translucent as to appro.ach transparency. The 

 egg, which is surrounded by a thin, smooth, 

 transparent shell, is as easily separated from 



