ON PAKAWRIGHTIA ROBUSTA. 



197 



species of Pevigouiiniis, while in Wriglitia it is white. 

 Oil the whole it appears advisable to separate it from 

 Wrig-htia; and the name Parawrightia robnsta is pro- 

 posed to indicate the relationship. 



II. 



The structures about to be described, and shown in situ m 

 PI. XXXIII, fig. 3, p./A, PL XXXIV, fig. 6, y.s., have only been 

 found in the male and female gonophores. I have searched 

 carefully in the substance of the general tissues of the hydroid, 

 both in the ectoderm and endoderm of the polyp, stem, and 

 stolon. Also, they have not been seen in any cavities, 

 such as the digestive cavities of the polyp or coenosarc, or 

 in the irregular cavities between the coenosarc and the 

 perisarc. The structures occur in the umbrella-cavity, in the 

 generative epithelium, and in one case embedded in the 

 ectoderm filling up the opening of the umbrella-cavity. 

 They have not been seen in the endodermal radial canals 

 of the c-onophore. It will be noticed that the structures 

 develop in temporary spaces, and that they must ultunately 

 pass out to the exterior by the dehiscence of the gonophore. 



In no sense do the bodies appear to exercise a malignant 

 effect on the host; they may increase in numbers in the 

 gonophore to a considerable extent, but the development of 

 the planula3 and sperm continues, to all appearance, in a 

 perfectly normal manner. 



From the amount of material available it is difficult to 

 obtain much idea of their frequency of occurrence. 1 have 

 collected six colonies ; three of these possessed no gonophores; 

 of the remaining three, two from one locality (Park Rynie) 

 were female, and one from another locality (Isipingo) was 

 male. About fifteen male and female gonophores in various 

 stages of development were present on these three colonies, 

 and the structures were present in ten. They occurred in 

 all three colonies, but not in every gonophore. The evidence, 

 as far as it goes, indicates a general occurrence of the struc- 



