336 



coral skeleton the "prototheka," or basal cup of the first individual of the 

 colony. x 



Lang (38) has written a very suggestive paper on growth stages of 

 British species of corals, in which he points out the fact that the onto- 

 genetic stages are repeated in each rejuvenescence (branching?), and sug- 

 gests that we have here an example of localized stages in development 

 (see Jackson 34). It may be remarked at this point that Ruedemann has 

 also detected localized stages in graptolites (47, 48), and Lang in Bryozoa 

 (36). Lang also, in the paper on corals, concludes that there is recapitu- 

 lation in the coral genera studied by him. of ancestral characters, and he 

 gives a table illustrating this. 2 



Summary. — Paleontologists almost universally accept the theory of re- 

 capitulation. Its chief critics have been embryologists. The reason for 

 the difference in attitude is probably to be sought in the fact that the 

 former ordinarily compare epembryonic stages with adult characters of 

 geologically older species, while the latter too often compare embryonic 

 stages with the adult stages of existing species. It is also to be noted 

 that in recapitulation we have to do with morphological and not with 

 physiological characters, and that the row of cells from the egg to the adult 

 may be morphologically the same in two organisms, while being at the 

 same time physiologically different. Until it can be shown that two organ- 

 isms morphologically different in the adult must of necessity be morpho- 

 logically different at all stages, the argument of Montgomery, Hurst and 

 others proves nothing. 



1 The term prototheka was proposed simultaneously (January, 1904) by Ber- 

 nard and myself for the earliest skeletal structure of. the coral colony. We have 

 used it, however, in a slightly different sense. Bernard applies it not only to the 

 first individual of the colony, but also to the basal plates or cups of later indi- 

 viduals. I intended to restrict it to the basal cup of the first individual. The 

 references are as follows : Bernard, H. M., The prototheka of the Madreporaria, 

 with special reference to the genera Calostylis, Linds., and Mosleya, Queleh. Ann. 

 Mag. Nat. Hist., Ser. 7, vol. xiii, Jan. 1904. Cumings, E. R., The development of 

 some Paleozoic Bryozoa. Am. Jour. Sci., vol. xvii, Jan., 1904 (footnote, p. 74). 



2 This so-called rejuvenescence in corals appears to be a species of budding, in 

 which the bud is directly superimposed upon the parent. It is fission occurring in 

 a horizontal plane, as suggested by Bernard (14), and the new skeleton is in 

 direct continuity with the old. This is the same idea exactly as that advanced 

 by Ulrich some years ago (63) to account for the diaphragms of the Bryozoa 

 Trepostomata. In the case of the Trepostomata the zoceeium is frequently oper- 

 culate (ex. Callopora). and there is good evidence that the bud grows up through 

 the operculum hence leaving it behind as the floor of the new individual. 



