NERVE TISSUE IN THE LOWEST ORGANISM. 169 



cate as to be, under ordinary circumstances, invisible. 

 !N"or is it surprising that the difficulty of detecting 

 them has induced some to adopt the hasty and, it 

 must be admitted, unjustifiable, inference, that many 

 creatures which exhibit combined and complex mus- 

 cular movements are altogether destitute of nerve- 

 fibres, but that the nerve matter of their bodies exists 

 in a diffused and fluid state, or in the form of minute dis- 

 connected particles disseminated amongst the tissues. 

 I^ow, if the tissue of the ann. of an Actinia, or 

 sea anemone, be carefully examined after successful 

 staining, § 68, multitudes of minute oval bioplasts 

 (nuclei), taking different directions, will be observed 

 amongst the muscular fibres, as well as in the external 

 investment. The disposition of these would receive 

 explanation if they were connected together by deli- 

 cate threads. Here and there in a very thin specimen 

 a very delicate film can indeed be discerned passing 

 from one bioplast to its neighbours. A precisely 

 similar arrangement is seen upon the muscular tissue 

 of the suckers of the common starfish, in the skin 

 of the oxflake, and in the true skin of the leech 

 and earth-worm. In these last I have been able to 

 trace very distinctly the connection between the 

 bioplasts and the excessively delicate inter- communi- 

 cating threads, as well as to demonstrate the passage 

 of the finest fibres into unquestionable nerves. In 

 insects, and especially in the maggot and common 

 bluebottle, I have also succeeded in tracing the con- 

 nection. In the peripheral organs of the perfect fly, 

 and in many tissues of the mollusca, especially over 

 some of the muscles, I have been able to separate an 

 extremely delicate tissue, consisting principally of 

 nerve cells with very fine fibres passing from them, 

 and crossing and interlacing in every direction, con- 

 stituting what may be truly described as a nerve 

 membrane of extreme delicacy. We shall find in the 

 peripheral parts of the nervous system of man and 



