BIMERIA RIGIDA ISP. N. 11 



When the spermatozoa are ripe the distal portion of the 

 perisarc -envelope gelatinises, and the spermatozoa appear to 

 pass through this softened swollen portion (fig. 28, sw.pr.) 

 without any definite rupture occurring. It has been noticed 

 that tlie ectoderm of the gonophore forms a conspicuous 

 columnai- epithelium at the distal end (figs. 24 and 25, cl.p.), 

 forming a kind of covering-cap or " Deckenplatte " imme- 

 diately under the perisarc which becomes softened. It is 

 suggested that this epithelium produces a secretion which 

 causes the perisarc to swell and soften at the distal portion 

 which thus subserves the function of the operculum so 

 commonly met with in the gonotheca of the Calypto- 

 blastica. 



Systematic Position. — The only species of Bimeria which 

 are traceable in the available literature are the following : 

 Bimeria vestita Wright, British Isles; Bimeria gracilis 

 Clark, San Diego, Calif oimia; Bimeria robusta Torrey, 

 San Pedro, Calif ornia ; Bimeria franciscana Torrey, Saw 

 Francisco Bay; and Bimeria annulata [Nutting), Santa 

 Catalina Islands, California. Judging from the descriptions, 

 a branching hydrocaulus is present in all the above species, 

 but in B. rigida the hydrocaulus consists simply of the 

 hydranth-pedicels which spring directly from a slightly 

 branched hydrorhiza. The amount of extension of the 

 perisarc over the hydranth is variously described in the 

 different species ; but clear figures are not given except in 

 the case of B. vestita, where AUman shows the perisarc 

 extending around the proximal two-thirds of the hypostome 

 region. In none of the species are the tentacles capitate as 

 in rigida. 



The production of gonophores directly on the hydrorhiza 

 is only found in the new species. 



The peculiar characters of the present species are : 



(1) The simple nature of the hydrocaulus. 



(2) The great development of perisarc over the hydranth ; 

 it extends almost to the edge of the capitula of the elongated 

 tentacles, and over the whole of the hypostome region. 



