of Mollusks in Holotburiae. 35 



newly-discovered facts might be regarded. They do not admit of 

 further explanation, but must be considered as ultimate facts, by 

 means of which many other phsenomena, equally remote from 

 the ordinary course, but equally unquestionable, may perhaps be 

 explained. In the natural sciences, the inexplicable becomes by 

 observation the basis of our explanations. The origin of diiferent 

 species in the creation is an indubitable fact of palaeontology, but 

 remains in the region of the supernatural so long as the very act 

 of origin is not seen, and traced out into its elements. As soon 

 as this is possible, it ceases to be supernatural, and falls among 

 that higher order of phenomena, whose laws also observation will 

 one day discover. 



Whoso would give his imagination license to deduce a few 

 further consequences from my observations, might thus specu- 

 late : — Till now it has been an idle question, whether the hen 

 were created first or her egg; but from these observations it 

 seems to follow that the egg had precedence, and further, that 

 the semen of the cock existed before the cock. Further, might 

 he say, that if the egg be primordial, the semen is contempora- 

 neous with it. It is thence needless to suppose the origin of a 

 double being consisting of male and female united, because we 

 are led to suppose a primitive contemporaneous origin of 

 males and females. From these observations, he would say, it 

 is explicable how animals with separate sexes were created by the 

 origin of ova and semen close together at the same place ; they 

 do not arise in the air, nor in the mud of the sea, but in an or- 

 gan ad hoc within a pre-existing animal ; and by means of an 

 already present organic Artificer, who indeed for his own ends 

 produces like from like, but also, obedient to a higher law, works 

 in the history of creation according to laws of which we have as 

 yet caught no glimpse. 



Such might be the speculations of one who thought fit to make 

 my observations a basis for the discussion of general metaphysi- 

 cal questions. 



From my place as observer, I have simply to discuss all possi- 

 bilities ; but, as may be readily supposed, I repudiate all analogy 

 between my observations and the theory of the equivocal genera- 

 tion of intestinal worms, which has long since taken its place 

 in the category of errors. It is fortunate that these observations 

 upon Synapta were not made sooner, since they might readily 

 have disturbed the course of science, and have given origin to 

 confused notions. 



The discoveries of R. Wagner, Loven, Sars, Krohn, Van 

 Beneden, and Dujardin, upon the production of Medusae by 

 Polypes, have been very generally explained by the alternation 

 of generations, which certainly occurs, indeed, in the Medusae 



3* 



