THK SKlUTLAKlD-iE. 37 



DEVELOPMENT OF THE SFinVLAKID.K. 



t if 1l,- xi, i- cells.- A> in so manv respects the two families Plumularida' and Scr- 

 tularida' here show their close relationship. So far as I can determine there is no difference 

 between them in this respect, in all species of Sertularida' in which the matter has been inves- 

 tigated both the nude and female sex cells originate in the endnderm of the stem and branches, 

 or at least are found in this position at a very early stage. Weismann reports this to be true of 

 Sertidaria jnimila and .v, i-f<il<ir< H<i /////.:///< /</*, and I have found the same thing 1 in S, ,-fj//, ///',/ 

 jiniiiiiit, Ifi/ilriill HKiniii fiili-iitn. S, ,-fnliii': Ilii <-<iini>li .i-<t, I>!J>IHIK!,I fiilli/.r, I>!fil,,ix!,i /,-,',,< ,//'<//, and 

 . I/'/'- t'nniriii tiii'i/i'/n. These comprise all of the species that 1 have examined for the purpose. 

 The sex cells originating in the endoderm of the stem are carried into the developing gonangium 

 along; with the voting Mastostyle. or else migrate as do those of the Plumularida'. the pre- 

 sumption being in favor of the latter, although I do not know that the process has been 

 completely demonstrated. 



The development of the gonangium has been partially described in the case of l>/ji]txi<i 

 fiilln.i-. It seems that tin 1 process is, in general, the same as in the Plumularida'. 1 and the same 

 thing seems to be true in the development of the ovum and that of the colony as a whole. 



As already stated, there are no known sertularians that produce free medusa', nor do the 

 gonophores present any easily recognizable medusoid features. 



Weismann has found, however, the characteristic cell layers that are seen in the medusoid 

 forms, and this leads him to pronounce i lie srrtularian gonophore a very much degraded medusa, 

 an opinion that can not be gainsaid in the present state of our knowledge. 



SYSTEMATIC msrrssiOK 



Family SEUTULAKIIKE Fleming (modilied). 



Ti'oplimmne.- Hydrant!) with a conical or dome-shaped proboscis and a single verticil of 

 filiform tentacles. Ilydrotheca' sessile, adnate or more or less embedded in the hydrocaulus, 

 arranged definitely and in more than a single row.' j An operculum composed of from one to four 

 parts is almost always present. Nematophores wanting. 



(iaiKixHiii, . (ionophores inclosed in gonangia. and always producing ova or spermatozoa 

 without the intervention of a medusoid form. 



The family Sertularida', :1 containing as it does the longest known genera of calypteroblastic 

 forms, has been defined by a number of writers, the general tendency being, as would be expected, 

 toward a more and more strict delimitation of the group. The above definition is in substantial 

 agreement with the views of most of the present authorities. Taken as a whole, the family is a 

 fairly well circumscribed group, although it has points of contact with caiupamdarian forms 

 through the genus 77/ ///"*///'// //* Allman,' which agrees with the Campanularidse in having the 

 hydrothec-e supported on pedicels, and with the Sortularida' in the characters of its hydranths. 



'See Part I, pp. .",li-39. 



'All iippuivnt exception is found in /I'l'lnil/iiniiiin. where the buses of the hydrothee.-c are aliened ill a sinifle TOW 

 on the upper siilc of the branches. 1 1 ere, howe\er, the distal portions "f the hydrothec;e are bent alternately to the 

 ri-rlit and left, ami nematophores are never found. These characters' are siillicieiit to separate tin- L'enns Inmi the 

 family I'lumnlarid;e with which it \\as formerly associate.l. It- place in the' Sertularid.e has not I'eeii ciuestiuued by 

 any recent writer. 



3 Tlie original spelling of this wonl seems to have been Sertnlariade. The lirst time that it occurs is in A History 

 of British Animals, hy Klemiiii.', Edinburgh, ISL'S, p. ."iliS. .[olmston, in the 1 second edition of British Hydroid 

 /oophytes, Londoii. IS-tT. uses the same spelling', as does Alexander AL'a-six, in his Catalogue of N'orth American 

 Acalejiliic, CamliridL'e, lsi>.">. Hincks, in his classic work. I'.ritish Hydroid /oophytes, London, IMiS, p. L'^3, adopts 

 the Spelling Sertulariidte, in which he has been followed by a few I'.ritish and American writers. 



McCready, one of the pioneer American workers in this tield, introduces the spelling Sertnlarida-," in Is.'iS. in 

 \vhieh he is followed by l.oilis A^assix, in his Contribution to the Natural History of the I'niled States, 1 V, 

 p. 355, and Allman in several of his later works, and most of the present workers, both American and Knropean. 



*IIydroids, of the Gulf Stream, .Memoirs of the Museum "I ( "inparative Zoology, V. No. "2, 1877, p. 10. 



