838 THE TTATUEAL HISTOET REVIEW. 



parasitic worms. But a great light was thrown on this department 

 of zoology in 1835 by Von Siebold, when he gave to the world his 

 account of the formation of the embryo in Monostomum mutabile, 

 an apparently insignificant parasite of water-fowl. The full impor- 

 tance of Yon Siebold's researches was not perceived till 1842, in 

 which year Steenstrup produced his renowned essay ' On the Alterna- 

 tion of Generations.' The most interesting chapter in this essay 

 was devoted to the Trematode animals ; a chapter containing mauj 

 original observations by Steenstrup himself, and unfolding, with rare 

 ingenuity and boldness, the existence of a relation between various 

 forms previously supposed distinct, but now shown to be metagenetic 

 conditions of the same individual organism. Other investigators 

 soon entered the field. It would be vain here to attempt even the 

 most scanty survey of the discoveries effected in scientific Hel- 

 minthology during the past thirty years. But amid the many 

 illustrious names which reference to such discoveries must recall, 

 that of Siebold still holds the foremost rank. As was said in 1854,* 

 so may we say in 1865, that this great anatomist and embryologist is 

 " truly at the head of Helminth ology." 



Dr. Cobbold's work, to which we would now direct the attention 

 of our readers, is the first general treatise on the Scolecida ever 

 published in Britain, and, for this reason alone, claims notice. 



It is also gratifying to find a British publisher undertaking the 

 issue of a work so purely scientific. The * style' in which the book 

 has been produced is excellent. Its size (royal octavo), its toned 

 paper, its typography, and its illustrations all deserve admiration. 



Dr. Cobbold's treatise contains a large amount of collateral in- 

 formation which wiU be useful to medical men, more especially as it 

 discusses the pathology of verminous diseases and their treatment. 

 Still, this is not its primary object. Nor does it enter copiously 

 into anatomical and embryological details ; so that, although con- 

 venient for reference, and by no means destitute of original matter, 

 it will not, in any marked degree, advance the science of Helmin- 

 thology. But it fills up, nevertheless, an important gap in our 

 literature. It offers to educated persons ignorant of zoology, and 

 to those naturalists who do not interest themselves deeply in 



* By Dr. Waldo Burnett, in his translation of SiebokVs Anatomy of the 

 Invertebrata (p. 103). 



