110 THE ROYAL SOCIETY OF CANADA 



commonly there is no regularity in the arrangement. In the young 

 forms they may be very few in number but as development proceeds 

 the number is increased until there may be as many as 24 present. 



Gonosome. — Medusa buds, from 1 to 3, usually 2, are developed 

 a short distance below the tentacles. Before the.medusse are liberated 

 the tentacles have grown to a length equal to about half of the dia- 

 meter of the bell and the four radial canals are quite distinct. The 

 free medusae (about 2 mm. in diameter at the time of liberation), 

 are nearly globular in shape with an extensive velum. The red 

 manubrium may reach to the opening of the bell or even beyond it. 

 It is of greater diameter at the base than at the extremity. The 

 tentacles are each provided with a distinct cap. The umbrella is 

 extensively pitted. 



Color. — Pale pink. 



Distribution. — Departure Bay (Fraser) ; Nanoose Bay, near 

 Clarke Rock, Departure Bay, off Protection I., Friday Harbor. 



As stated in previous papers this species has been found only 

 within the branchial cavity of certain ascidians, attached to the 

 peribranchial wall. They are not confined to individuals of the same 

 species, however, as Dr. Huntsman records 1 specimens in Phallusia 

 ceratodes, Ascidiopsis paratropa, Ciona intestinalis and Tethyum 

 aurantium. 



Many good specimens have been obtained and the development 

 has been traced until the medusae were liberated but no medusae 

 were found large enough to possess even an indication of gonads, 

 consequently there is no certainty as to the size when they leave 

 the ascidian, as they surely must do, and no information whatever 

 as to how or why the planulae seek such a base for attachment when 

 the proper time arrives. In the case of the majority of hydroids 

 apparently anything solid will serve for such attachment but in this 

 species there appears to be a high specialization in that regard. 



No specimens have been found earlier than June 5. At this time 

 there were small individuals with small tentacles 4 or 5 in number, 

 but many were full grown with medusa-buds well developed. Colonies 

 obtained on October 17 contained no very young individuals but some 

 of the medusa-buds were still small while others were fully developed 

 and the medusae were being set free. 



Family Clavidae 



Trophosome. — Hydranths with scattered filiform tentacles. 

 Gonosome.— Gonophores producing sexual products in fixed 

 sporosacs. 



'Ascidians from the coasts of Canada. Trans. Canadian Inst., 1911, p. 116. 



