382 



of their characters when found on land, and in dry places and dry 

 seasons are often found in the perfect form so extremely small, 

 that there can be little doubt these too like frogs and toads are occa- 

 sionally reproduced without first going through the larva state. * 



A remarkable case of altered instincts in a small species of spider 

 (Neriene errans) found in coal mines is mentioned by Mr. TufFen 

 West. In its natural state this spider is met with in fields about 

 the time of hay-harrest, and is only known as a solitary wanderer, 

 making no web of any kind, further than a few scattered lines. In 

 the coal-pits, into which they are supposed to have been carried 

 down originally by accident with the provender for the horses, they 

 become gregarious, and live in large colonies, constructing sheets 

 of web of vast size. Mr. West saw one 30 feet long by 4J feet 

 wide, hanging from about the middle of the roof t 



Another striking instance of animals accommodating themselves 

 in time to locahties not originally natural to their organization and 

 habits, was that noticed some years back by Professor Loven of 

 certain Crustacea occurring in the Swedish lakes, which had pre- 

 viously only been known as marine species inhabiting the Arctic 

 and Baltic seas. The explanation of it was thought to be " that 

 the gradual elevation of the Scandinavian Peninsula had cut oflF 

 these originally marine creatures from their natural habitat, and 

 that they had been able to accommodate themselves successfully to 

 altered conditions of hfe." X This fact is suggestive, and should 

 not be lost sight of by those who study the productions of our 

 fresh waters, whether fish or any lower forms of animal Ufe, 

 especially waters commxmicating with the sea or not far distant 

 from it. 



Instances such as the above might be adduced to almost any 

 extent, in proof that the habits of animals are dependent mainly 

 upon outwai'd circumstances. But we will now confine ourselves 

 to those more particularly connected with the subject before us. 

 Among the vertebrate animals the class of birds is that which to 

 the local naturalist will open up the widest field for observation. 

 The mammals, fish, and reptiles, found in a limited district, such 



* See Man. Brit. Vert. An., pp. 304-305. 

 t Rep. Brit. Assoc. 1861. Sections, p. 163. J " Nature," vol. i., p. 455. 



