specimens (j/Oeplialodiscus densus. 439 



tliose vvifcli two testes, and those with an ovaiy and a testis. 

 The gonads vary in their state of maturity in different zooids. 

 The young" ovaries are rather longer and straighter than 

 those figured as C and D in text-fig. 7 of the ' Terra Nova' 

 Report (i6^ p. 46), and tlie pigment-granules around the 

 oviducal aperture are bhack rather than red. In tlie material 

 in the smaller bottle, received from Prof. M'lutosh, all the 

 zooids that were examined had ripe gonads. Free ova occur 

 in this material ; they are found among the buds, in the 

 deeper end of the coenoecial tube, there being not more tlian 

 one ovum in any one tube. The ova are free, and not 

 attached by a stalk ; they measure 0*9 mm. in length and 

 0'6 mm. in width, and the two ends are similar. In two 

 cases where a free ovum was present in the coenoecial tube 

 among the tangle of buds it was found that the zooid in- 

 habiting the tube was hermaphrodite, and the ovary and 

 testis were both ripe (cf. i6, p. 47, and 17, p. 23). It would 

 be interesting to ascertain if a free ovum ever occnrs in a tube 

 inhabited by a male zooid — probably not ; the present material 

 is too limited in bulk to permit of a more extended search in 

 this direction. 



The greatest number of buds found attached to any one 

 zooid is eighteen ; this group includes buds of all stages of 

 develo|)ment, from the very young stage before the appear- 

 ance of the red line of the shield up to a large bud with small 

 tentacles appearing on the arms (c/. 16, p. 47, text-fig. 8, C 

 and k). Tlie youngest buds, however, are not buds of the 

 main zooid, but arise from the side of the extremity of the 

 stalk of a large bud — that is to say, the larger buds begin 

 producing the next generation of buds before separating from 

 the parent zooid. The laigest bud of the group of eighteen 

 just mentioned had two small buds of its own. 



References. 



(i) Andersson, K. a. "Eine Wiedereiitdeclcung von Cephalodiscus.'" 

 Zool. Anz. xxvi. 1903, pp. :5G8-369. 



(2) . "Die Pterobranchier der Schwedisclien SiidpoLir-Expe- 



dition, 1901-1903." Wiss. Ergebii. IStjliAvedisclieu Siidpolar- 

 Expedition, v. (Stockholm, 1907) pp. 1-122, 8 plates. 



(3) Gravikr, C. "Suv line espece uouvelle de Cephalodiscus {C. an- 



derssoni, nov. sp. ) proveHaiit de la Seconde Expedition Autavctique 

 Franfcaise." Bull. Mus. Hi>l. Nat. Paris, 1912, xviii. 3, pp. 146- 

 150, 2 text-finures. 



(4) . ' Deiixieiue Expedition Antarctique Franfaise, 1908-1910; 



Sci. nat., Documents scientifiques ; Pterobranclies.' Paris, 1913, 

 pp. 71-86, 5 text-ligures. 



(5) Harmer, S. F. ''On new Localities for Ce/>Aa/o«?«scMS," Zool. Anz. 



xxvi. 1903, pp. 593-594. 



(6) . " The Pterobranchia of the 'Siboga' Expedition, with an 



