376 W. K. BROOKS ON THE LIFE-HISTORY 



canals, bnt my observations show that the development of our Liriopeis, in all essentials, 

 like that of the European Geryonidae. 



Our species appears to be very regular in its breeding habits, and specimens captured 

 at all hours of the day laid their eggs at about 8 p. m., the eggs passing out of the 



mouth. Fol says that when he kept female specimens of Geryonia fungiform!* by 

 themselves they did not lay their eggs, but that as soon as a mature male was placed 

 with them and discharged the contents of his reproductive organs into the water, the 

 females at once deposited their eggs (22). 



This was not the case with our species, for when I placed a single female by itself it 

 discharged its eggs promptly at the proper hour. In two or three cases these eggs were 

 not fertilized and soon died, without exhibiting any evidence of vitality, but in other 

 cases the eggs laid by an isolated female developed normally. Schulze has shown, how- 

 ever, that hermaphrodite Geryonidae sometimes occur, and these females may possibly 

 have been hermaphrodites; but the occurrence or absence of fertilization makes no dif- 

 ference in the time of oviposition. 



The eggs develop very rapidly and at six o'clock the next morning the embryos are 

 in the stage shown in PI. 9, fig. 3, so that it is necessary to keep them under observa- 

 tion all night in order to study the early stages. The segmentation of the egg 

 and the formation of the ciliated embryo have been correctly and very minutely de- 

 scribed by Fol (22) and by Metschnikoff; and, as is well known, the origin of the 

 germ-layers is very peculiar and without any exact parallel. The transparent spherical 

 egg, which consists of a peripheral layer of granular protoplasm, and a central less 

 granular portion, in which the protoplasm is finely reticulated, undergoes total regular 

 segmentation, and gives rise to a spherical embryo, composed of a single layer of larger 

 cells, arranged around a small central segmentation cavity. 



Each of these cells consists of an internal transparent reticulated portion, and an outer 

 more granular portion, PI. 41, fig. 1, a + b. Soon the outer granular portion, fig. 1, a, 

 separates from the transparent portion b, leaving this as an independent endoderm cell 

 inside the layer of ectoderm, which is formed from the outer granular ends of the blas- 

 toderm cells. This division of each blastoderm cell into a central endodermal cell, 

 and an outer ectodermal one, does not take place in all parts of the egg at the same 

 time, and eggs may easily be found in the stage which is shown in fig. 1, where two 

 distinct layers are present on one side only. The central cavity, the segmentation cav- 

 ity, persists, and ultimately becomes converted into the chymiferous tubes, and the 

 stomach of the adult medusa. Before the delamination of the blastoderm cells is com- 

 pleted, the ectoderm cells begin to multiply by division, and the ectoderm cells of the 

 young embryo are therefore more numerous than the endoderm cells, which divide more 

 slowly. At the end of the process of delamination. the embryo, fig. 2, consists of a 

 continuous hollow spherical layer or shell of granular and slightly flattened ectoderm 

 cells, fig. 2 a, and within this, and in contact with its inner surface, a second concen- 

 tric hollow sphere, c, of large transparent rounded endoderm cells, with reticulated 

 protoplasm, surrounding a small centra] digestive cavity, d. The gelatinous substance of 

 the umbrella now begins to appear between the ectodermal shell and the endodermal one, 

 thus stretching and flattening the ectoderm cells, which continue to increase in liuin- 



