321 THE NATURAL HI3T0ET REYIEW. 



SO that they can be apprehended only in imagination, or by recourse 

 to unaccustomed metliods of research, the interest of the inquiry 

 becomes doubled. Thus it is that some feeling, stronger than a 

 " cold, wondering," intellectual spirit, urges us to investigate, alike 

 the extinct forms of past times, and the unseen fauna and flora of the 

 microscopic world. From this point of view, if from none other, does 

 Helminthology display attractions equal to those of Paleontology, or 

 of the science of minute organisms. 



It is true that, with many persons, these creatures only excite dis- 

 gust ; partly by reason of the outward aspect of some, but chiefly 

 because of associations derived from their peculiar habit, and the 

 diseased conditions which, in certain cases, they produce. Hence the 

 ignorant and prejudiced, who care little for natural history in general, 

 care still less about the study of parasites. Professor Owen, com- 

 batting such prejudices, has termed the Helminths " outcasts " of 

 the animal kingdom.* But the external appearance of several 

 parasites, especially of the more minute forms, is, assuredly, not 

 repulsive ; while the internal organisation of all, as revealed by 

 dissection, presents an arrangement of parts which it would be no 

 misuse of language to term beautiful. Nay, some are so transparent 

 that, without any dissection whatever, their structures, under the 

 microscope, show themselves with such exquisite distinctness as to 

 banish at once all feelings save those of delight and curiosity. Even 

 among the more obviously disgusting species, as the tape-worm or 

 common Ascaris, the vulgar sensations at first aroused by their 

 apparent loathsomeness are quickly effaced whenever we commence 

 the study of their morphology and development. We deprecate, 

 therefore, as weak, and unworthy of so accomplished a zoologist, the 

 sentiment which makes M. De Quatrefagesf declare that he will spare 

 his readers " the technical details in endeavouring to convey some 

 portions of a history, which touches on the most important questions 

 in general and philosophic physiology." 



Of internal parasites, some are vegetable, some animal ; and, of the 

 latter, most would find a place in the sub-kingdom Annulosa. Again, 

 of annulose parasites, a few are Arthropods, as the ' bot * larvae 

 among Insects. But the great majority belong to that vast assem- 

 blage of lower annulose forms, generally denominated Worms. 



* Lectures on the Invertebrate Animals, 2nd ed. p. 58. 

 t English translation of " Les Metamorphoses," p. 202. 



