PODOCORYNE AREOLATA. 33 



appearing of different lengths from their varying contrac- 

 tility ; the incrusting base from which the polypites rise, 

 a solid chitinous expansion"*, bearing simple linear spines 

 in groups, having areolar spaces between them ; GONO- 

 PHORES sessile on the base, large, globular, or slightly 

 pear-shaped, containing each a single zooid. 



GoNozooiD. UMBRELLA (at the time of liberation) sub- 

 globose, moderately deep, covered with thread-cells ; 

 MANUBRIUM rather long and columnar, but not extend- 

 ing beyond the margin of the umbrella; RADIATING 

 CANALS golden-yellow, continued by four rather short 

 marginal tentacles with bulbous bases, one to three 

 shorter tentacles in each interradial space, the number 

 varying with age. 



Height of polypite about -^ inch. 



PROF. ALLMAN has constituted for this species the genus 

 Rhizocline, which he ranks amongst the Hydractiniidce. 

 From this decision I am compelled to dissent. The H. 

 areolata of Alder is a true Podocoryne, presenting all the 

 essential characters of that genus as defined by its 

 founder, Sars. 



The mere fact of its producing its gonophores on the 

 stolon instead of the body of the polypite cannot entitle 

 it to generic rank, for we meet with the same variation 

 within the limits of a species. Nor is there anything 

 peculiar in the nature of the incrusting base. Mr. Alder 

 describes it as a " solid chitinous expansion ; '' but in its 

 origin it is no doubt a reticulated stolon, the meshes of 

 which are gradually filled in with chitine, as is the case 

 in Podocoryne carnea^. The gonozooid of H. areolata 

 agrees with that of Podocoryne in all essential particulars. 

 In Mr. Alder's specimens the number of tentacles was 1G ; 



* In an early stage this is probably represented by an open network, 

 t Mr. Alder agrees with me in my interpretation of this portion of (In- 

 structure. 



1) 



