100 



EMBRYOLOGY 



ance by the interpolation of new small septa in regular order 



between the existing' ones. 



Non-sexual reproduction in the form of fission and huddlng 



is found widely distributed in the Zoantharia ; by this means 



extensive colonies are developed 

 in the skeleton-forming Corals 

 (Sclerodermata), whereas in 

 the group of non-skeletal Ac- 

 tiniaria (Malacodermata) the 

 individuals produced by fission 

 or budding usually separate 

 entirely, so that, with few ex- 

 ceptions (Zoanthea?), the forms 

 in this case remain solitary. 



Fig. 46.— Basal plate of a larva of 

 Afiroidex cfitycularis, soon after at- 

 tachment, with twelve radial riflges 

 (^after Lacaze-Ddtbiebs, from BAt,- 

 fouk's Comparative Emhvijology). 



Budding in the Actiniaria has been 

 observed more rarely — Epiactis 

 (Verhill, ?), Gonactinia (Blochjiann 

 UNI) Hilger), Zoanthus.. More fre- 

 quently reproduction takes place by 

 fission. This may divide the parent 

 animal into two nearly equal parts: either as Jongitudinnl Jission, which 

 begins at the oral disc and progresses toward the base, or takes the oppo- 

 site direction, or as transverse division, a kind of reproduction which has 

 been described in detail for Zonactinia prolifera by M. Sars and by 



Fig. 47.— Two stages of transverse fission of Gonactinia prvUfera, Sabs (after 

 Blochmann vhd Hilgbk). 



Bloch.mann UNI) Hilger (No. 74), and which in its outcome presents strik- 

 ing resemblances to the divisions in Flabellum and Fungia described by 

 Semper, and to the process of strobilization in the Scyphozoa. In Go- 

 nactinia it is always young animals that undergo transverse division. 



