60 



MORPHOLOGY. 



well developed on both edges. The processes which are thus developed on the edges of the 

 leaflet are in all respects similar to the lateral nematophorcs of tlie trophosome (see p. 28). 

 They are filled, like these, with soft granular protoplasm, in which is immersed a cluster of fusiform 

 thread-cells, and which is in direct communication with the coenosarc filling the cavity of the 

 leaflet. They are also, like these, perforated at their extremity by an oblique aperture ; but I 

 have never seen the nematophorcs of the corbulas emit, like those of the trophosome, pseudo- 

 podial prolongations of their contents. 



Fig. 30. 



Development of the Corbula iu Aglaoplien'ia pluma. 



A, Very young corbula; B, corbula more advanced; C, corbula in a still more advanced stage; D, the mature 

 corbula; E, transverse section of mature corbula, sbowing two gonangia, each containing a single gonophore. a, a, 

 leaflets of corbula; h, h, gonangia; c, ramulus supporting the leaflets; d, a hydrotheca. 



F, Separate leaflet from mature corbula. a, continuation of the somatic cavity into the leaflet, where it divides into 

 two branches, & J ; c, nematophores forming tootb-like processes on the distal edge of the leaflet ; d, imperfectly deve- 

 loped tooth-like processes on the proximal edge; e, septum, dividing the cavity of the leaflet, 



G, Gonangium from mature corbula. a, continuation of somatic cavity into gonangium ; 5, blastostyle, partially 

 suppressed by the enlarging gonophore ; c, gonophore ; d, spadix ; f, ovum ; g, wall of gonangium. 



As the young leaflet continues to grow, its cavity becomes partially divided by a cliitinous 

 septum (F(?) which stretches across from the outer to the inner side, parallel to the axis of the 

 leaflet, but always nearer to the proximal edge. At the free end of the leaflet the septum is 



