INVERTEBEATE ANIMALS. 83 



Space is here deficient, but some of the more 

 remarkable forms are exhibited, including Gasteracan- 

 tha and Acrosoma, with bodies armed with long spines 

 and glittering during life with brilliant metallic colours. 

 Estimated number of species, 1220 (Walckenaer) ; 

 British, 303 (Blackwall). 



IT Small series of British Spiders presented by J. 

 Blackwall, F. L.S., author of "A History 

 of the Spiders of Great Britain and Ireland. ' * 



Upper Compartment. 

 About 14 species of Mygale, ^vyciXri, a Field-mouse ; 

 tubular nests of Mygale, shewing the trap- 

 door ; female Mygale, with egg-cocoon, &c. 



Class INSECTA. 



Head, thorax, and abdomen distinct ; antennae a single pair ; 



three pairs of legs borne on the thorax. 



The species included in this*^ wondrous class have been 

 estimated at 160,000 in number, which is about equiva- 

 valent to the sum of the species in the whole of the rest 

 of the Invertebrate Animals, together with the Fishes, 

 Eeptiles and Amphibians, Birds and Mammalia, with all 

 the known species of plants in addition. In other 

 words. Insects constitute about one-half of the spe- 

 cies included in the Animal and Vegetable Kingdoms. 

 (Mr. Bentham's Presidential Address to the Members of 

 the LiNN^AN Society, 1871.) 



The chief orders of the class have long been pretty 

 well established on characters mainly derived from the 

 organs of flight ; but all attempts to collect the orders 

 into higher divisions have hitherto been unsatisfactory. 

 By far the most important scheme divides the class into 



