HYDUOZOA. 



1m. i. 15. 



Case 4. 



efficicucy even on old dried specimens. The degenerate dactylozooids Cumo *. 

 have a number of capitate tentacles, while the giustruzotiids have only 

 a whorl of four (Fiij. 1(1). 



In isoi Prof, llickson discovered the male, and in Ihkh the 

 female ^ledusa (Fig. 17) of Jlillpjiont in small «;apsules, which. «lien 

 occurring near tlie surface, form rounded swellings (auiiiulhu.*). 

 Latterly, ^Ir. Duerden has seen the living Medu.sae in his aquarium 

 ut Jamaica. This tiny Medusa is only about -^^ inch in diameter ; 

 its cavity is nearly filled up by the large manubrium containing the 

 eggs. The umbrella is devoid of canals, tentacles, and sense-organs, 

 but is provided with batteries of thread- 

 cells ; and usually no mouth can be 

 seen at the end of the manul)riuni. 

 The little creature, however, is able to 

 swim away with its heavy burden t)f 

 eggs from the parent colony ; having 

 deposited the eggs, it shrivels up. 



STYLASTEiiiDiE. In this family the 

 dactylozooids are without tentacles, and 

 one or both kinds of zooids are supported 

 in their calicles by a calcareotis style. 

 There are several genera in this family. 



In Stijlaster the pores are arranged 

 in " cyclo-systems " — a circle of dacty- 

 lopores surrounding a central gastropore. 

 A cyclo-system presents a deceptive 

 resemblance to the calicle of an ordinary 



coral ; in the latter the calicle contains one coral polyp, but in the 

 cyclo-system there are a do/.en or more degenerate individuals sur- 

 rounding a central individual; the dactylozooi<ls were formerly 

 supposed to be tlie tentacles of the central zooid. The generative 

 buds, which are situated in the often numerous swellings or ampullae, 

 never become free Medusa3. 



The Stylasters are remarkable for the elegance and beauty of 

 their arborescent fan-shaped forms (Fig. 1 and tluir excjuisiie 

 colouring. Several specimens of Stylastir rosn/s from off a cable 

 from the West Indies show considerable variation in colour, l»eing 

 white, rose-pink, and salmon-colouicd. The cyclo-systems regularly 

 alternate on the sides of the slendri- liraiu-hes. 



Fragment f>f MiUfMtra, sluiw- 

 ing the cirdcB otcmctyloporeu 

 each with 11 coiitnil p;a8tri>|>->rf . 

 (Twice natural size.) (After 

 Mosolev.) 



' From •' Kucyclopivdia Brituniiiea." 



