ONIDARTA 



101 



Somewhat below the middle of the parent animal is formed a circle of 

 bud-like projections, out of which is developed the circle of tentacles of 

 the lower individual. While the upper part is being constricted off, the 

 oral disc and the oesophagus of the lower off- 

 spring of the division are developed. Finally, 

 the upper part detaches itself. It appears that 

 both parts have the power to divide again. 



Another remarkable, more widely distributed 

 kind of division, which had already been ob- 

 served by DiCQUEMAEE and by Dal yell (No. 4), 

 has recently been studied in detail by A. Andhes 

 (No. 73), and has been called laceration (Fig. 

 48). This consists in the abstriction of frag- 

 ments of a basal expansion. At the margin of 

 the base of an Actinian a small part is character- 

 ized by the opacity of its entoderm and by its 

 firm adherence to the support, the latter being 

 caused by a secretion of the ectodei'm. By the 

 contraction of the parent animal, the modified 

 marginal part is torn away from it. This can 

 now be metamorphosed either directly into a 



small Actinian, or after further separation into 



smaller fragments. 



Both kinds of non-sexual reproduction, fission 



and budding, are widely distributed among the 



Corallia. Thej' here lead to the formation of 



extensive stocks of various shapes. In many 



cases (Oculinacea and Astrfeacea) in which it 



was formerly believed that lateral budding 



occurred, Studeb (Nos. 94 and 95) was able to 



show, upon closer investigation, that there exists 



a reproduction by fission, one of the resultants 



of division coming with further growth to 



occupy a position on the lateral wall of the 



other part. A similar kind of reproduction has 



been observed among the Fungiaceaj in Her- 



petolitha limax. 



Genuine basal budding is found, for example, 



in Turbinaria, where the base of the colony 



exists as a common plate of coenenchyraa, at 



the margin of which new individuals bud ; like- 

 wise in Galaxea. 



The form of longitudinal fission occurring in the Corallia, which 



usually begins with a constriction of the oral disc, may remain more or 



less incomplete, so that the individuals remain united with one another 



in series. This arrangement can be recognized even in the skeleton, since 



Fig. i8. — Reproduction 

 in Aiptasia lacerata by 

 means of abstriction of 

 a basal part (after A. 

 Andres). A to C, advanc- 

 in? abstriction ; D, E, 

 metamorphosis of the 

 fragment into a small 

 Actinian. 



