72 



THE CYSTIDEA 



diplopores ; the anus close to the peristome, and with a valvular pyramid ; 



small hydropore, perhaps combined with gonopore, between mouth and 



anus, to the left ; five orals 

 separated by food -grooves 

 with primitive bilateral 

 arrangement. The various 

 species may be arranged 

 groups, according to 



Flo. XXXVIII. 



Sphaeronis globulus, after Angelin. 1, from side, nat. 

 size ; 2, tegmen, enlarged. 



n 



the number of times the 

 grooves branch, and the 

 number of brachiola given 

 off from them. Haeckel 

 (1896) has sought to separ- 

 ate as genera (Pomonites, 

 Pomocystis, Pomospliaera) 

 those with one, two, three, 



and four brachiola to each ray ; but until Angelin's notoriously 



inaccurate figures shall have been corrected by observation instead 



of by hypothesis, these names can rest on no sure ground. Moreover, 



Love"n's figure of the type- 



species, S. pomum, repro- 



duced in our Fig. XXXIX., 



shows that the number of 



branches visible may be 



two, three, or four in a 



single individual. Eu- 



cystis, Angelin (1878), Or- 



dovician, Sweden (Fig. 



XL.), sends its grooves 



farther down the theca 



than Sphaeronis, over one 



or two circlets of thecal 



plates. From the distal 



end of each ray a brachiole 



was given off, while others 



of uncertain number and 



position arose along the 

 side of the grooves. Prob- 

 ably some of the forms 

 described by S. A. Miller 

 as Holocystites should be 



BT 



A s 



FIG. XXXIX. 



Ad oral region of Sphaeronis pomum (from Loven, "Om 

 placed here (e.g. TrematO- Leskia mirabilis," Ofv. Vet.-Alcad. Forhandl. 1867, p. 434). 

 riitt'it Taplrp^ a 1th mi oh ' orals coverin g mouth ; vg, section of food-groove running 

 cysns, jaeKCi;, aitEOUgn from mou t h to B/, brachiole-facets, some of which are pierced 

 their orals are not known, by an axiaj canal ; ^4s, plates closing over anus ; G, pro- 

 TT . -\r-\-i e n -, minence with two pores, which Loven considered gono- 

 H.gynnus, Miller & Lrurley pores; M, ridge which Loven thought might indicate a 

 C\ ftQ4."\ r>rppnt n atirro ir> madreporite (or G may represent combined gonopore and 

 (1894), presents a Stage in hydro ore) . diplo p 0re ^ su iound the whole area. 



the development of food- 

 grooves that in some respects is more advanced, although the peristomial 

 plates have no regular arrangement (Fig. XLIL). Allocystis, Miller (1889), 



