8 Goel. 
CCELENTERATA. 
larva; (2) the Athorybia stage ; (3) the larva like the adult, but 
possessing provisional structures. The present paper deals with the 
growth of the egg from fertilization to the primitive larva.. 
G-otte (17) gives some interesting details of the development of Aurelia 
and Cotylorhizci , and comes to the following conclusions : (1) The coelo- 
gastrula of these Scyphomedusce is effected by the immigration of the 
endoderm into the cavity of the coeloblastula. (2) The Scyphistoma is a 
perfect Anthozoon, owing to the discovery by the author of the iuvagi- 
nation of the ectodermal oesophagus and the occurrence of gastral sacs 
and septa surrounding it. (3) The Ephyra , and consequently the Scypho- 
medusa, is a metamorphosed Scyphistoma , or Anthozoon, just as the 
Hydroid Medusa is a metamorphosed Hydroid Polyp. 
MTntosh (35) states reasons for regarding Cyanea lamarcidi , Per. & 
Les., as an immature stage of C. capillata , Esch. No reason for the 
change of the deep blue of the former into the brown of the latter is 
suggested. [ Cf . Zool. Rec. xxi. Ccel. p. 9.] 
Metschnikoff (39) describes the early development of CaUianira bialata , 
Beroe forshalii , and B. ovata. The gastrulation is at once embolic and 
epibolic, the plan of construction is regular, and the blastopore oral. The 
Ctenophores, alone of Coelenterates, seem to have a mesoderm which 
appears as a definite layer in the embryo ; so far as the author observed, 
the mesoderm arises from the endoderm alone, and not also from the 
ectoderm. 
General Biology. 
Dana (9) reviews the various theories which have been framed to 
account for the origin of coral reefs. The Darwinian theory and its 
evidences is restated, with additional proofs. The objections raised by 
Semper, Rein, John Murray, A. Agassiz, Geikie, and others, are severally 
met, and the conclusion is arrived at that “ the subsidence which the 
Darwinian theory requires has not been opposed by the mention of any 
fact at variance with it, nor by setting aside Darwin’s arguments in its 
favour ; and it has found new support in the facts from the ‘Challenger’s’ 
soundings off Tahiti that had been put in array against it, and strong 
corroboration in the facts from the West Indies.” In his travels the 
author was made to see a system of arrangement in the Pacific Islands, 
to appreciate the vast length of the island chains with their many paral¬ 
lelisms, and the accordant relations subsisting between them and long 
lines of atolls. He was thence led to observe the corresponding system 
in the features of the continental lands. “ Thus a conception of the 
earth as a unit became early implanted, and the idea also of its develop¬ 
ment as a unit under movements as comprehensive as the system in its 
feature lines.” 
H. O. Forbes (Naturalist’s Wanderings in the Eastern Archipelago 
[London : 1885], p. 40) inclines to believe “that the Cocos-keeling reef 
foundation has arisen as Murray, Semper, and Agassiz have suggested ; 
but that its islets have been the result of the combined action of storms 
and the slow elevation of the volcanically upheaved ocean floor, on 
which the reef is built.” 
