vol.l] Torrey. — Hydroida of the Pacific Coast. 27 



man ('71) is the continuation of the perisarc so as to invest the 

 proximal portion of each tentacle. Allman adds that the peri- 

 sarc also covers the hypostome to within a short distance of the 

 mouth. 



I have examined specimens of (lamia annulata Nutting from 

 the collection which contained the type of his species, and find 

 that they are similar in all respects to a hydroid from the 

 entrance of San Francisco Bay. These San Francisco speci- 

 mens were carefully examined to determine the presence or 

 absence of perisarc on the tentacles. It was extremely difficult 

 to make out the distal limit of the perisarc. It is certainly 

 attached to the ccenosarc, thinning away distally very gradually. 

 Soaking in caustic potash destroyed more than the distal half of 

 each tentacle, and demonstrated that the basal portion of each 

 was sheathed in delicate perisarc, as shown in Fig. 1 , PI. I. Repeat- 

 edly have I seen the perisarc continue upon the bases of the 

 tentacles in the expanded living hydranth. It is by no means 

 an "opake brown" (Ilineks, '68, p. 103) nor is it so conspicu- 

 ous and its distal limit so clearly marked as in Allman's figure 

 of B. vestita ('71, PI. XII). But these cannot be considered 

 differences of generic importance. Neither do I think that the 

 extent of the perisarc offers any Longer a proper criterion for the 

 separation of the two genera. The tentacles of B. vestita are 

 alternately elevated and depressed; those of G. nutans and the 

 present species are not. This character by itself, however, is 

 not even of specific importance. 



While the trophosomes do not offer distinguishing characters, 

 the gonosomes of these genera are held to be distinct for two 

 reasons: first, the gonophore is "borne on the summit of a true 

 branehlet, where it takes the place of the hydranth on an ordi- 

 nary branehlet" (Allman); second, the perisarc of this branch- 

 let expands below the gonophore into a sort of cup (Nutting). 

 The Alaska and San Francisco specimens agree in possessing 

 gonophores, some of which are completely covered with perisarc, 

 as in the typical Bimeria, and lack the proximal cup-like expan- 

 sion, while others are left half naked by the rupture and retrac- 

 tion of their perisarcal covering, and still others possess what 

 approximates the cup-like expansion that Nutting describes. 



