72 



THE CYSTIDEA 



A 6 



Fio. XXXVIII. 



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

 size ; 2, tegmen, enlarged. 



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 

 in groups, according to 

 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, Pomosphaera} 

 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 Flo X xxix. 



as Holocystites should be A doral region of ' Sphaeronis pomum (from Loven, "Om 



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



riistijt TflpVp^ nltlinnrrh orals covering mouth ; vg, section of food-groove running 



Cl/StW, Jaefcei;, altnougn from mou j. h ^ B/, brachiole-facets, some of which are pierced 



their orals are not known, by an axial canal ; As, plates closing over anus ; G, pro- 



IT TV/ril s n i minence with two pores, which Loven considered gono- 



Jtl. gynnus, Miller & hurley pores; AT, ridge which Loven thought might indicate a 



(1894), presents a Stage in '"^reporite (or may represent combined gonopore and 

 hydropore) ; diplopores surround 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 (1 889), 



BT 



