288 ZOOPHYTES. 



planula. By anticipation I may here cite, for a much stronger resemblance, 

 the spinula from the ovum of the ascidian race. 



In doing so it is not to dip more deeply into the theory already 

 glanced, which considers the source of the fertility of every ovum as de- 

 rived from the union or incorporation of one of the mysterious animalcula 

 above named with it. 



Certainly it is very extraordinary to witness so remarkable a resem- 

 blance to the tadpole, in such a number of animals in an early stage. 



But, to assume that the invisible animal — one of its ten thousand 

 fellows, belonging to the male, imparts life by its incorporation with the 

 ovum of the female, and that from thence subsequent enlargement, evolu- 

 tion, and metamorphosis, for maturing a perfect being, shall ensue, has no 

 shadow of probability. 



In the genera above named, the Sertularia and the Ascidia, the form 

 of the ovum resolves into the resemblance of the tadpole, the former less 

 definitely than the latter. 



Thus, without presuming to controvert the opinion of those profound 

 physiologists, maintaining that the microscopic tadpole is instrumental in 

 so wonderful a part, I most humbly doubt, in infinite deference to them, 

 whether the consequent is not substituted for the antecedent ; whether 

 the early course of metamorphosis does not resolve into the microscopic 

 form, instead of that microscopic form preceding the commencement of 

 metamorphosis. 



It is difficult, indeed, to reason satisfactorily on either side, where 

 experiment can offer so little aid, or rather none, and regarding which 

 even the unassisted senses of mankind fail of imparting knowledge. 



The ancient maxim, Omne animal ex ovo, " Every animal comes from 

 an egg" is far from fallacious. It may be duly appreciated in numberless 

 examples, from animals at a certain stage. Did the microscopic tadpole 

 fertilize the otherwise sterile ovum, the maxim would be inverted. On 

 the whole, it seems more natural to presume that the host of animalcula 

 found in so peculiar a medium as their dwelling, originates as the animalcula 

 mfmoria ; that they belong to a multitude of ova, so minute as to escape 



