118 INTRODUCTION TO CLASSIFICATION. 



organs are developed either singly from its base, or arise from 

 the common body. When free-swimming reproductive zooids 

 are developed, they are craspedote Medusas. 



The immediate product of the growth of the embryo is a 

 free Calycophoridan or Physophoridan Polype. 



3. The DISCOPHORA. The immediate product of the growth 

 of the embryo is a fixed polype provided with tentacles arranged 

 on the circumference of the body, at some distance from the 

 mouth. When free-swimming reproductive zooids are produced, 

 they are developed by transverse fission from this primary form, 

 and consist of a disk or umbrella, devoid of any velum, from the 

 centre of which the gastric apparatus depends. This is called 

 an acraspedote, or steganophthalmous, Medusa. 



Lucernaria, Cyantea, Rhizostoma, and their allies constitute 

 this order. 



Not improbably a fourth order will have to be added to 

 these three, for the Trachymeduste of Haeckel. 



IV. THE ANNULOSA. 



The arrangement of the class INSECTA into orders is hardly 

 to be regarded as complete at present, but several groups are 

 very clearly distinguishable from one another. These are 



1. The COLEOPTERA, which are provided with mandibles and 

 maxilla? adapted for masticatory purposes. The wings are 

 rarely absent ; when present the anterior pair are converted into 

 horny or leathery elytra, which are not used in flight, and serve 

 during rest as covers to the posterior wings. These are mem- 

 branous and can be folded up longitudinally and transversely. 



Metamorphosis is complete ; a quiescent pupa stage, in which 

 the limbs of the pupa are free, being interposed between the 

 active larva and the sexual, or imago, state. 



This order contains the Beetles, Cockchafers, Weevils, etc. 



2. The HYMENOPTERA have mandibles and maxilla? adapted 

 for biting and cutting. The first pair of maxilla? may be produced 

 into knife-like blades, and the second pair into a sucking pro- 

 boscis. Both pair of wings take part in flight, and are alike 

 membranous, transparent, and reticulated. In the females 



