CNIDARIA 



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 jiart detaches itself. It aj^pears that 

 both parts have the power to divide again. 



Another remarkable, more widely distributed 

 kind of division, which had already been ob- 

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

 has recently been studied in detail by A. Andres 

 (No. 73), and has been called luceraiion (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 ectoderm. 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 i-eproduction, fission 

 and budding, are widely distributed among the 

 Corallia. They here lead to the formation ot 

 extensive stocks of various shapes. In many 

 cases (Oculinacea and Astrteacea) in which it 

 was formerly believed that lateral budding 

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

 show, upon closer investigation, that there exists 

 a rei^roduction 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 ccenenchyma, 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. 48.— Reproduction 

 in Aiptasia lacerata by 

 means of abstriction of 

 a basal part (after A. 

 AifDRBsJ. .4 to C, advanc- 

 ing abstriction ; D, E, 

 metamorphosis of the 

 fragment into a small 

 Actinian. 



