31 G The Caddis-Worm and its Houses. 



of caddis-worms iuto their reservoirs as a means for their 

 extermination. 



Now after all that has been stated on the variety of struc- 

 tures of caddis cases, it should be borne in mind that however 

 great may seemingly appear to be the difference between the 

 different cases, such as between the wicker-work house of tho 

 caddis and that which was made from the teeth of a tortoise- 

 shell comb, yet the general design of those houses is iden- 

 tically the same. For instance, if they be compared together 

 it will be seen that all the cases are made of the same shape, 

 namely, in that of a tube, and that the same smooth surface is 

 found to exist in the interior of those houses. The .. only 

 difference between them consists in the manner in which the 

 pieces of the material are arranged, and not in the design of 

 the whole. The design upon which the case is made is derived 

 from instinct, which is implanted into the organization of the 

 creature by nature, which leads them to construct cases of 

 such a uniformity of plan as was said in an analogous case 

 by Gilbert White, in his Natural History of Selborne, that 

 " The God of Nature is their secret guide." As soon as tho 

 creature is hatched it commences building a house without 

 experience and without knowledge, and without even requiring 

 to be taught, and which is as perfect in its structure as if it 

 had the most extended experience and the most correct know- 

 ledge, and the same plan will also bo observed in all instances. 

 lustiti'-f then does not proceed from the operations of the 

 niind, but is something which is implanted into the nature 

 of the creatures as a part of their organization, and which 

 causes them to act upon that idea that has been implanted. 

 With respect, however, to the choice of each stone, the 

 caddis is guided by a particular adaptation of each piece for 

 its purpose, and to that extent acts as well as man could do 

 under similar eireiimstanees. Whilst I lie design of thfi ease is 

 clearly instinel ive, as nineli reason is shown ilt -the choice of 

 materials as man could exercise under the same conditions. 



In these pages I have endeavoured to point out, simply the 



principal features of that wonderful instinct which is possessed 



by the larvie of that order of insects commonly known as 

 e.iddi .-•-worms. The facts which I have mentioned wore all 



ertained by trying experiments with them. Blor, as 

 I have said at the commencement of this paper; the ex- 

 periments were carried on solely from an intense desire to 

 I. now what were; the Capabilities of these curious creatures. 

 !!ut I feel convinced thai more can lie learnt of them, and it 

 is in the hope that, others may he incited totho Same object, 



that this account, has been written, which contains that which 

 I myself have lea rut through my own observations made upon 



