126 NATURAL SCIENCE. Feb.. 



slightly from that of Linne. As he points out, the most serious 

 difficulty in the arrangement of insects in orders is presented by the 

 Linnean Neuroptera. This "order" he prefers, though provisionally, 

 to keep intact, in spite of the vast difference in metamorphosis 

 shown by the groups composing it. It cannot be denied that such 

 conservatism is convenient, but it might have been well at least to 

 have separated the mayflies from other "Neuroptera" (as well as the 

 earwigs from the Orthoptera), the paired genital openings in these 

 groups being surely an archaic character of high import. It is hard 

 to accept Dr. Sharp's objection to the use of such characters on the 

 ground that but few insects have been examined for them. Zoology 

 can only proceed on the assumption that the correlation of certain 

 external structures with certain internal structures will be found to 

 hold throughout a natural group. A museum ornithologist will not 

 hesitate to class a new skin with feathers and beak as an egg-laying 

 bird, though it is but a presumption that the living creature did lay 

 eggs. The peculiar structure of the mouth-organs in caddis-flies, 

 also, seems to warrant ordinal rank for them. Dr. Sharp, though 

 restoring the Linnean name of Aptera for the Collembola and 

 Thysanura objects to Brauer's grand division of insects into winged 

 and wingless. Many of the "winged" insects, he points out, have 

 no wings. But surely the idea of the division is that in the one 

 group the absence of wings is a primitive character — in the other 

 secondary. 



The orders of Insecta described in detail in this first part of the 

 work are the Aptera, Orthoptera, Neuroptera, and Hymenoptera, as 

 far as the Trigonalidae. This arrangement is certainly open to 

 criticism, for if any two orders of insects should be brought closely 

 together, the Lepidoptera should follow the caddis-flies. And 

 Dr. Sharp admits that the Hymenoptera have good claim to stand at 

 the head of the insect-world — therefore to come last, if the Aptera 

 begin the series. 



But the way in which Dr. Sharp treats the details of his subject 

 is, as in the introductory chapters, admirable. One is especially 

 struck by the balance which is maintained all through between 

 various branches. In the account of each family, external form, 

 morphology, development, habits are all adequately dealt with and 

 excellently illustrated ; while the more solid matter is diversified by 

 discussions on such points as the power of the book-louse Atropos to 

 produce " death-tickings," and the hypocritical devotions of the 

 Mantids. On every subject, while old authors are not neglected, 

 references to the latest work are given. The anatomist will find a 

 summary of Grassi's recent researches on the Thysanura ; the lover 

 of insect habits, the same naturalist's observations on the Termites ; 

 the systematist, descriptions of Hansen's Hemimerus and Simon's blind 

 cockroaches from the Philippine caves ; the lover of controversy, a 

 notice of Spencer and Weismann on the sexes of ants ; while foot- 

 notes on every page will send off the industrious student to consult 

 the original monographs. 



In his treatment of families. Dr. Sharp is rather inclined to 

 "lump." For him all dragon-flies are but one family, all caddis-flies 

 but one. These views do not seem to be at present those of naturalists 

 who have specially studied the groups. It is remarkable, however, 

 that in many orders, after a period of splitting into numerous families, 

 has come a time of reunion. This has been the case with moths, 

 beetles, and bugs, and it is possible that Dr. Sharp's views of the true 

 value of family groups in other orders to-day may become those of 



