THE MUSCULAR SYSTEM. 31 



In describing Insects the vertex, or crown, of the head is the 

 highest part ; and the front is the part usually in front of fhe 

 insertion of the antennte. 



The Mlsculak System lies just beneath, and is continuous 

 with the integument. It consists of numerous "distinct isola- 

 ted straight fibres, which are not gathered into bundles united 

 by comnron tendons, or covered by aponeuroses [or tendinous 

 sheaths] to form distinct muscles, as in the Vertebrata, but 

 remain separate from each other, and only in some instances 

 are united at one extremity by tendons." (Newport.) These 

 minute fibres form layers, which Newport regards as separate 

 muscles. "Each fibre is composed of a great number of very 

 minute fibrillar, or fasciculi of fibrillar," and has been observed 

 by Wagner and Newport to be often striated as in Vertebrates. 

 The muscular system is simplest in the lower insects and the 

 larvae of the higher forms, and is more complex in the head 

 than elsewhere, and more complex in the thorax than in the 

 abdomen. These minute muscles are exceedingly numerous. 

 "Lyonnet, in his innnortal work on the anatomy of the larva 

 of Cossus lignrperOa. found two hundred and twenty-eight dis- 

 tinct muscles in the head alone, and, by enumerating the fibres 

 in the layers of the different segments, reckoned 1,647 for the 

 body, and 2,118 for the internal organs, thus making together 

 3,993 muscles in a single larva. In the larva of Sphinx Ikjus- 

 .tri we have found the muscles equally numerous with those 

 discovered by Lyonnet in the Cossus." (Newport.) 



The muscular system corresponds to the jointed structure of 

 insects, as do the other internal systems of organs. Of the 

 muscles belonging to a single ring, some stretch from the front 

 edge of one segment to the front edge of the next, and others 



of the Scorpion, who?e mode of development appears to bo precisely similar to 

 that of a telson. In the same category we must rank the lahnini in front of the 

 mouth, which in the Crui^taceu (at least) appears to be devel.>pod from the sternum 

 of the antennary, or third somite, the metastoma (or so called labium, or lingua) 

 of Crustncett, and the lingua of Iiisecta, behind the oral aperture. 

 ' " However much these appendages may occasionally simulate, or play the part 

 of appendages, it is nni)ortant to remember, that, morphologically, they are of a 

 very dilVere'it nature, and that the confusing them with true appendages must 

 tend completely to obscure the beautiful relations whi-'h obtain among the dif- 

 ferent classes of the Artkulata:'- Huxley, Linnxan Transactions, vol. xxn. 

 London- ' 



