﻿Is Selaginopsis mirabilis a Native of British Seas 219 



gonangium (Fig. 1). This short branch is abnormal in 

 bearing, instead of six rows of hydrothecse, only four rows, 

 each hydrotheca-pair being set at right angles to the pairs 

 immediately above and below it, as in Staurotheca. Such a 

 meristic variation, which represents the normal development 

 of Selaginopsis cylindrica (Clark), where the proximal 



Fig. 1. Portion of stem of Selaginopsis miraMlis, with branch arising from 

 interior of gonangium. x 40. st. =stem; br. = branch ; gon. = 

 gonangium. 



portions of the branches bear four rows of hydrothecae, the 

 distal six (or rarely eight), is unusual in Selaginopsis 

 mirahilis, although in this species also there is occasionally 

 manifested a tendency for the hydrothecae situated at the 

 base of the branches to be fewer in number and less definite 

 in arrangement than those further from the origin. 



A duplicated hydrotheca represents a type of variation 

 which I have not hitherto observed in Hydroids. A single 

 hydrotheca is replaced by two (Fig. 2), but the cavities of 

 the twin cells are continuous, although a partition running 



