THE PLUMULARIP/E. 



30 



each a distinct nucleus and micleolus. The ova become aggregated in certain portions of (lie 



interuodes immediately below the places where 



the gonangia are to appear, but are, of course, 



muchlarger and lessnumerousthanthe sperraa- 



toblasts in the male colony (fig. 104). Tbe go- 



nangia originate as already described. After 



the young gonangium has pierced the perisarc 



and has been followed by the ectoderm, stutz- 



lamelle, and endoderm, the ova migrate with 



definite cell movement into the blastostyle 1 



(fig. 104), after which they reassemble, as it 



were, in. the developing gonophore. While in 



this position they actually diminish in number, 



many of them being apparently reabsorbed. 



Next the ova penetrate the stutzlamelle and 



take their position between it and the endo- 



derm. The present writer was so fortunate as 



to obtain a section showing an ovum which 



had just broken through the stutzlamelle, the 



fracture still being evident (fig. 104). It seems, 



however, that the stutzlamelle was already un- 



dergoing repair, as there was an indication of 



an exceedingly delicate membrane forming over 



the fractured spot. 



During the maturing of the ovum the cover 

 plate of the gouangium diminishes, and is finally 

 penetrated by the escaping plauuln. A second 

 gonophore is often formed, the ova making their 

 appearance in the blastostyle, and not migrating 

 from the stem joints. In Aiiiennuhiria there is 

 but one gonophore in each gonangium and a 

 single ovum in a gonophore. 



The following species of lMiunularid;e have 

 been investigated with the view to determining 

 the origin of the sex cells, and in all cases these 

 elements appear to originate in the stem. De 

 Yarenue, however, reports finding them in the 

 body of the hydranth. 1'lumularin echinitlata, 

 Plumularia halecioides, Anteniii/liiriit antennina, 

 and AglaopJienia pliona were studied by Weis- 

 maun; Plumularia fragilis and probably other 

 species were studied by Ilamann; Fluiniihir'ut 

 ecli in ttlata was studied by I >e Yarenue ; 2 Plum u- 

 laria echinulata, Plumultn-ln pinnntd, Tlumiilu- 

 ria lialeeioides, Plumularin ,iiiiiilin, Antennularia 

 janini, Aglaophenio plinnn, and Aglaophenia Jiel- 

 leri were investigated by the present writer. 



Development of the corbvla. Weismann is 

 the only one, so far as I know, who has described 

 the very beginning of the development of the 

 corbula, although the later stages have been 

 investigated by others. According to the first-mentioned writer, the s<-x cells arise in the 



106 



OEKilX OF THE OVA IN rLl'MrLARID-E. 



Fig. 1U4. Loii{!itiiiliii:il sei'tinii of |>artcif stnu aud base of goDaiisiiiui 

 <if riiuitiiliiriii erliiitulalti, xlimvingovain tlio rnclciilenu oftln- ifin 

 ;iml of tlio liliistnat.vlc. f, i-iivity <if Ma^tc.^tyli-; c , i-avity of sti-ni 

 ,,i ova; J'. jirl-isarr nf ^Mtiilll^iiliii : /' |i"i is.-irr of >ti-lil. 



Kig. 105. Aiiotlier part of Niinir M-riion. showing ova in endoderm nf 

 stein. 



Fig. 100. (Hilii|iir wrtion :u I'osH tliu base of the hlaatostyle of ,l;;(a- 

 plteiihi lirlleri, lii>wini; :ni ovum wlm-li INIS :i]>p:in-nt!y just lir"ki-n 

 tlin.u^li thu stulxlaini'llr al lir. r, raxityol lilatci.-tj Ic ; eft, ctn 

 derm. m. eniloilcnn \villi (lev. loping ova; 11, niu'lons: n', nurlco 

 Ins : nf, n\ ii in ; ji. p. 'i M:H < /- | H-ri save ot c'i >rl .u l.i ; t 1 ?, wttlt/lanirl!.-. 



'Hamanii say s that this movement resembles that ..fam..-!,:,-. 

 Zeitschrift fiir Natiirwissenschaft, XV, ISSL', p. 30.) 



- Kecherches sur la Reproduction <le^ l'nly|..-s Myilrnirex, 1SSL 1 , p 



(D.-r or^Hiismns ,1,-r Hydroidpolypen, Jenaisehe 



