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latter class, the worst of all parasites, that he proposed to speak. 

 Nor eonld colour be taken as a test of classification, as the- 

 colours were as varied as the colours of the lainbow. Nor could 

 the defining line be that <>£ usefulness or otherwise ; for, before 

 they had travelled far, they would founder on some all-important 

 but hidden rock. He proposed to confine himself by the aid of 

 photomicrographs to some of the better-known varieties of parasitic 

 insects. I'he fii-st division had been aptly termed " lodgers." 

 The lodgers make use of their host as a dwelling-place, 

 sometimes using the host for a short time only, and then 

 vacating the establishment for one more suited to their require- 

 ments. Amongst this large group may be found the barnacles 

 attached to the skin of the whale ; or the sea anemone, who 

 frequently prefers the shell of the hermit crab, or shells of similar 

 character, to that of a more solid basis, so that its diet may be 

 varied by its bring carried to pastures ever new. Again, we 

 have a very large number of sponges, as well as a number of tube 

 worms, who attach themselves to inhabited shells of various kinds. 

 In this latter case we may look upon the tube worms as permanent 

 lodgers, as, prior to building their establishmeut, they make the 

 foundations very firm upon the surface of the shells they intend 

 to reside upon. Many also of the po'.yzoa are to be found 

 amongst this class, as was well illustrated by Dr. Gabbett in his 

 interesting lecture lately delivered before this Society ; whilst, 

 if time would permit, a very great variety may be enumerated a* 

 living under similar circumstances, examples of which may 

 be found upon our beach with each receding tide, or in 

 the pools amongst the rocks at low water. The second 

 group were not only " lodgers," but also " boarders " in 

 the truest sense of the word, expecting their host not 

 only to supply apartments, but also a liberal table. These all 

 breathe oxygen, and it may be interesting here to see the 

 wonderful provision of the Great Creator in their elaborate breath- 

 ing apparatus. Though they have mouths and many of them are 

 provided with powerful lancets and marvellous pieces of apparatus 

 for the purpose of feeding, they do not use their mouths for 

 breathing purposes. In the insects themselves there are no true 

 lungs, but wonderful pi- ces of apparatus whereby the air is 

 circulated over the body. Thus we find scattered all over the 

 body a number of minute openings, frequently covered by fine 

 hairs, which have the power of n.oving so as to prevent any 

 objectionable substance passing into the openings. These 

 openings are known as spiracles and are the true breathing porea 

 of the insect. On dissecting one of these we find connected with 



