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THE BRITISH NATURALIST. 



2 53 



first. It is not with a wormlike movement that it advances. It has 

 legs, though they are very small, and cannot be properly seen without 

 the aid of a powerful glass. These legs are one of its peculiarities. 

 They are attached to its back, that is the side opposite to the stomach. 

 The insect continually lies on the back, and its mouth is turned 

 upwards. This last circumstance is not peculiar to it. We know some 

 species of flies and aquatic insects that always swim on their backs 

 because they feed on insects that swim or walk on the surface of the 

 water. We shall soon see that for a similar reason it was necessary 

 that our insect should always have its head turned upwards. Its legs 

 are short and formed something like the last legs of silkworms." 



For a long time we were firmly of opinion that M. de Reaumur was 

 correct as to the two anterior pairs of pseudopeds being attached to the 

 dorsal side, even after two lots of living specimens had been sent me by 

 Professor Miall, but M. de Reaumur was certainly wrong in the rest of 

 his description of the legs, for he clearly mistook the long setae, with 

 which the other segments were furnished, for feet. I don't wonder very 

 much at this considering the very inferior apparatus which the old 

 Frenchman had to use, for these curious creatures are almost impossible 

 to examine with nicety, as they will not keep in the water of the 

 zoophyte trough but constantly force two-thirds of their body, that part 

 containing the sixth segment, upwards through the top film of the water, 

 either along the sides of the glass or up the stalks of the water plants. 

 Besides, this description was fully confirmed by the old Swedish 

 naturalist, Baron De Geer (" Histoire des Insects," vol. 6, page 380), 

 who was the first to give the life history and metamorphosis of the larva. 

 When, however, I had overcome the difficulty of translating from 

 Danish the next description by Dr. Stceger, : " I found that he had 

 satisfied himself that these two pairs of false feet are on the ventral 

 side of the body, and that the creature has not its feet on the 

 back of its neck, as I at first thought, long before I found out M. de 

 Reaumur's account. This has been more recently proved by ribbon 

 sections cut by Professor Miall and myself, which show that the ventral 

 nerve cord runs on the same side as the pseudopeds. These I hope to 

 show later on by reproducing the micro-sections. The arrangement of 

 the ventral setae is very peculiar, those near the head being inclined 

 towards that organ, while the others are inclined from the sixth seg- 

 ment towards the tail. The smaller setae on the dorsal side of the 

 fifth, sixth, seventh, and eighth segments incline in both directions, 

 according as the end of the segment is towards the head or the tail. 

 We can now follow M. de Reaumur once more. 



" Now the animal being doubled in two, though its legs are differently 

 inclined with respect to the head, they are turned towards the same side 



* Page 202, "Naturhistorisk Tidslkrift," Cophenhagen, 1842-3. 



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