ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 217 



to this, however, Shipley attaches little importance, while as to the 

 origin of the mesoblast, he points out that a similar history is found 

 in Echinoderms, Enteropneusta, Chordata, and probably Peripatus. 



The author does not think that the Brachiopoda and Polyzoa form 

 together a natural phylum; he would rather follow Gegenbaur in 

 making a " primary class " of the Brachiopoda, allied to MoUusca, but 

 more nearly to Vermes. 



Arthropoda. 

 o. Insecta. 



Genealogy of Insects.* — This paper, by Dr. A. S. Packard, jun., 

 commences with a diagram illustrating the author's views on the 

 phylogenetic relations of the various groups of insects to each other. 

 The lowest group is that of the Thysanura, and the genus Scolopen- 

 drella, with its abdominal true legs, probably comes nearest to the 

 hypothetical ancestral form. The Dermatoptera, Orthoptera, and 

 Pseudoneuroptera present in the larval condition more or less close 

 resemblances to Thysanuran genera, and have probably originated 

 from some such forms. The origin of the Coleoptera may probably 

 be traced to some form like Campodea ; and the arguments for this 

 view are the form of the larv» of the carnivorous beetles, especially 

 of the Carabidse, Dytiscidse, and Staphylinidfe, which display on the 

 whole a more primitive type than those of other beetles ; in the phyto- 

 phagous larva3 the mouth-parts become more aberrant, and often 

 show a tendency to become aborted ; and in the weevils the head, 

 mouth-parts, and legs undergo a gradual degradation and atrophy ; 

 the phytophagous forms are therefore evidently more specialized 

 and less like the ancestral form than the carnivorous species. The 

 first larva of the oil-beetle (Meloe) is very like a Campodea ; the 

 second larval stage closely resemble'^ a larval Carabid ; the third 

 larval stage is again closely similar to the larva of one of the lamel- 

 licorn beetles ; and, finally, the fourth stage with aborted mouth-parts 

 and legs recalls the larva of the weevils. The metamorphosis of 

 this insect is a kind of shortened epitome of the development of the 

 Coleoptera from some Campodea-like ancestor, and the resemblances 

 of its four larval stages to the larvae of the other Coleopterous genera 

 are stated in a tabular form in Dr. Packard's memoir. Palseonto- 

 logical data are, however, not quite in harmony with this view, since 

 the earliest known beetle is a weevil (the most specialized type) from 

 the carboniferous rocks. 



It is also possible that some metabolous Neuropteron may have 

 been the ancestor of the Coleoptera, and the close resemblance of the 

 larva of Gyriuus to the larva of Corydalis and other Sialidae favours 

 this view. The three higher orders, Diptera, Lepidopter and a 

 Hymenoptera, had probably a common origin in the Neuroptera ; the 

 larvse of saw-flies and the caterpillars of Lepidoptera are both very 

 like Panorpid larva3 ; and the maggots of Diptera, especially the 



* Amer. Natural., xvii. (1883) pp. Q32--4.5 (2 figs.). 

 Ser. 2.-V0L. IV. Q 



