10 ERNEST WARREN. 



directly by the liydrorliiza on short pedicels of about '08 mm. 

 in length (text-fig. 1, sp.). The pedicels are not distinctly 

 annulated. The dimensions of the gonophores vary con- 

 siderably ; the measurements of three were : '45 x '30 ; 

 •35x'24; -31 mm. x -18 mm. 



The gonophore represents a medusa, but no umbrella- 

 cavity is formed during development, and in the adult 

 gonophore there is only a single layer of ectoderm, instead of 

 a layer covering the spadix and a layer lining the inside of 

 the perisarc, as would occur in the case of a more highly- 

 developed gonophore. 



The spadix in the adult gonophore has endoderm branches 

 springing from it, which run through the spermatic tissue 

 towards the periphery (PI. II, figs. 25, 26) ; these endoderm 

 branches are met by a small cluster of elongated ectoderm 

 cells (c. ec.) which are continuous with, and form part of, the 

 ectoderm lying just within the perisarc layer. 



In the youngest gonophores no genital cells are observable 

 (PL II, fig. 21). When slightly older scattered genital cells 

 (fig. 22, g.) in the ectoderm can be noticed. These cells have 

 not been seen to migrate from the endoderm of the hydro- 

 caulus or liydrorliiza, and apparently they arise in situ. 

 The genital cells become concentrated in clumps (fig. 23) 

 and active proliferation takes place, forming compact masses 

 of spermatocytes separating the ectoderm from the"endoderm 

 of the spadix (fig. 24). The gonophore continues to grow as 

 a whole, and the endoderm remains adhering to the ectoderm at 

 certain places, and there the endoderm becomes drawn out into 

 diverticula (figs. 24 and 25, e. d.) which are connected with the 

 ectoderm layer by the elongated cells (o. ec.) above mentioned. 

 Ultimately growth ceases and the spermatocytes undergo the 

 last division into spermatozoa (fig. 27, spz.), and soon clumps 

 of ripe spermatozoa with tails [r. sp.) can be seen. During 

 the proliferation of the spermatocytes the endoderm cells of 

 the spadix increase in size and project into the coslenteron in 

 a swollen condition^ and the nuclei become enlarged (cf. 

 figs. 24 and 25). 



