38G SEA-SIDE STUDIES. 



of thought, not in originating new. To assume a new atti- 

 tude of thouglit, it may be necessary to develop new fibres ; 

 and this cainiot be done in a tissue already too fibrous. A 

 ■similar hypothetical explanation suggests itself for the for- 

 mation of fixed ideas, monomanias, habits, and tendencies. 



But I wUl not venture further into this hypothetical region ; 

 the few anatomical facts hitherto ascertained presenting too 

 narrow a basis for such speculations. One cmbiyological 

 indication may, however, be added. The nerves of insects 

 are, it is known, distinctly fibrous (although in the bee and 

 locust I have observed the fibres occasionally melting into 

 mere granules), but in the larvae of insects the nerves are 

 often mostly gi-anular. Thus in the active predatory Dra- 

 gonfly Larva — the water-tiger, as it is called — I found the 

 great ventral chord possessing distinct fibres, but in many 

 places it was purely gi'anular, the granules not having even 

 a linear disposition.* In the preparation I have made of 

 this object a veiy interesting analogy between the develop- 

 ment of nerve and muscle is presented. Muscles are of two 

 kinds, striped and unstriped, the former being generally, but 

 erroneously, called voluntary, the latter involuntary muscles. 

 According to recent researches, it has become evident that 

 the striped muscle is only a more differentiated form of the 

 unstriped, there being several intermediate stages between 

 the two.f lu tlie jjreparation I have made of the ventral 

 chord of the dragonfly larva, this is strikingly exliibited. 

 A fragment of muscle is attached, the fibrillar of which, in- 



* In more advanced Lan-ao these chords arc wholly fibrous. 

 + Leydig, llistoloijie, p. 43. 



