REPORT ON THE SIPHONOPHOR^E. 147 



Each of the two nectophores has in general the form of a kidney or bean, with a 

 deep longitudinal sulcus or groove at its ventral side, corresponding to the hilus of the 

 kidney. This furrow is the hydrcecial sulcus (fig. 4, ni) included between the two 

 lateral longitudinal wings of the bell [nx right wing, and nl left wing, in figs. 2-7). In 

 the middle of this groove, in the ventral median line of the nectophore, arises its pedicle, 

 a small triangular vertical plate (fig. 4, np). The proximal apex of the triangle 

 (fig. 7, np) connects the bell with the top of the siphosome (fig. 4b, a). The dorsal or 

 abaxial side of the nectophore, as well as its lateral sides, are equally rounded, without 

 crests, and the two ventral nearly parallel longitudinal wings are its only edges. The 

 jelly-substance of the umbrella is, as in the other species of the genus, extremely soft and 

 nearly diffluent, so that the bell, taken out of the water, loses its natural form. 



Nectosac. — The nectosac, or the subumbrellar cavity of the nectophores (figs. 5-7, w), 

 is relatively larger than in the other species of the genus hitherto described. It occupies 

 nearly the aboral half of the umbrella, whereas in the latter it takes up only one-third or 

 one-fourth of it. The form of the nectosac is sometimes campanulate or ovate (figs. 1,6), 

 at other times hemispherical or subglobular (figs. 2, 5). Its axis is not identical with the 

 longitudinal axis of the reniform bell, but inclined towards it at an acute angle. The 

 basal opening of the nectosac is circular and surrounded by a broad velum (figs. 2, 6, v). 



Canals of the Nectophores. — A short peduncular canal (figs. 5, 6, cp) passes from the 

 top of the siphosome immediately to each nectophore, obliquely ascending in the apical 

 bell, descending in the basal bell. The peduncular canal runs through the lamellar 

 pedicle of the nectophore obliquely to the top of the nectosac, and gives off in this 

 course two vertical blind pallial canals or " mantle-vessels," an ascending and a descending. 

 The superior or ascending mantle-canal (figs. 2-7, cs) runs vertically upwards towards 

 the top of the bell, near to the apical edge of its triangular peduncle, and may be 

 regarded as the homologue of a somatocyst. The inferior or descending mantle-canal 

 (figs. 2-7, cs') runs in the opposite direction downwards, between the basal edge of the 

 peduncle and the ventral canal of the nectosac, parallel to the latter. The four canals of 

 the nectosac, which arise from the distal end of the peduncular canal, are arranged in two 

 pairs of very different length and form. The ventral (cv) and the dorsal canal (cd) are 

 nearly equal, and lie in the sagittal plane, following the simple curvature of the nectosac, 

 whereas the two lateral canals (ex right, and cl left) are twice as long as the former, and 

 form in their course a double sigmoidal loop ; they descend from the top of the nectosac 

 curved towards the dorsal face, then are bent twice downwards and twice upwards, and 

 finally reach the circular canal near the ventral face (figs. 2-7). 



Hydrcecium. — There is no true hydrcecium or funnel cavity in the genus Praya, 

 but the two deep ventral grooves of the two opposite nectophores, or the funnel-furrows, 

 (fig. 4a, 4b, ni), are so turned one to another, that there is formed a cylindrical hydrcecial 

 canal, open at both ends. Its smaller apical half, with the upper aperture, is empty ; its 



