192 
POPULAR SCIENCE REVIEW. 
•on those best suited to the public mind. It is the latter view which M. 
Van Beneden has taken. And in our opinion the choice has been a perfectly 
wise one. For it must be remembered that the book is not a strictly 
scientific one, but, on the contrary, is intended for the man who has scientific 
tastes without scientific knowledge. Therefore the whole style and tone of 
the present work are in adaptation to the wants of the general reader. If 
there is one defect in M. Van Beneden’s observations it is that he seeks in 
some cases to be pleasant in style at the expense of conciseness of language 
and clearness of thought. 
In the first instance we must take exception to the author’s division of 
parasites, which seems to us to be a perfectly artificial one, and one too 
which, however well it may look on paper, does not hold water as a practical 
mode of grouping. He divides all parasitic animals into Messmates, Mutualists , 
and Parasites, and the last he groups as parasites free during their whole 
life, parasites free while young, parasites free when old, parasites that migrate 
and undergo metamorphoses, and lastly parasites during their whole life. 
Under these several headings he supplies a vast amount of information, 
occasionally illustrated — but it must be confessed imperfectly — in which he 
gives an excellent and popular account of the singular vagaries of the various 
parasites. Talking of the wanderings of the individuals which make up an 
entire cestoid worm, he says that recently Herr Leuckart, in concert with 
M. Mecznikow, has discovered u transmigrations of worms accompanied by 
changes of sex ; that is to say, they have seen nematodes, the parasites of 
the lungs of the frog, always female or hermaphrodite, produce individuals 
of the two sexes which do not resemble their mother, and whose habitual 
abode is not within the lungs of the frog, but in damp earth. In other 
words, let us imagine a mother born a widow, who cannot exist without the 
assistance of others, producing boys and girls able to provide for themselves. 
The mother is parasitical and viviparous, her daughters are during the whole 
of their life free and oviparous.” 
M. Van Beneden might well have given us more information on the 
subject of the Gregarince than he has furnished; the paragraphs supplied 
being extremely brief and not by any means exhaustive. However, with 
this and one or two other instances of neglect, the author has performed a 
■difficult task with admirable skill. He has told us many wonderful and 
truthful tales, and has brought so much humour to bear on the subject, that 
’he has made many unusually dull questions sparkle with the wit and viva- 
city with which he has surrounded them. 
FIKST BOOK OF ZOOLOGY.* 
f|lHEBE is in this little work a considerable amount of originality exhi- 
X bited, both in composition and illustrations. The book too is luxuriously 
got up as to type and paper. With these remarks our friendly criticism 
* “ First Book of Zoology.” By E. S. Morse, Ph.D. Henry S. King 
& Co. 1876. 
