276 CLASS vm. 



The reproductive power in Insects which undergo metamorphosis 

 is wanting in their perfect state ; but if at an earlier period in 

 the state of larva they have lost a foot, it grows out again at the 

 next moulting, and is more or less perfectly restored. Also in the 

 Myriapoda excised antennae grow again 1 . 



The nervous system of Insects has for central part a row of 

 ganglia of different number, which are usually connected with one 

 another by two threads that are often very intimately united. This 

 row of ganglia is situated on the ventral surface beneath the intes- 

 tinal canal in the mid region of the body ; the first ganglion however 

 lies in front of and above the oesophagus, and there arises, by reason 

 of the two threads which connect it with the second ganglion, a 

 ring which surrounds the oesophagus. The greatest number of 

 ganglia is found in the Myriapoda, eighteen in Lithobius (Scolop&ndm 

 forficata), twenty-three in Scolopendra morsitans. In the larvae of 

 butterflies thirteen are counted, but ordinarily they are less numerous 

 in the hexapod Insects. Large ganglia are situated in the thorax, 

 and in some there are none in the abdomen, but two nervous strings 

 alone, sometimes close together, sometimes separate from each other, 

 as in Nepa and Cicada. From the ganglion above the oesophagus 

 (ganglion cerebrate] arise the nerves of the eyes and antennas ; this 

 ganglion lies transversely on the oesophagus, formed of two oval or 

 somewhat conical lateral portions with their broad part turned to 

 each other ; the inferior surface is somewhat concave, the upper 

 convex. The second ganglion, the first of those beneath the intestinal 

 canal, is by some writers compared to the cerebellum, by others, OBI 

 better grounds, with the medulla oblongata; the nerves that arise 

 from it proceed to the oral parts, and perhaps correspond to th^ 

 different branches of the fifth pair in vertebrate animals. Earlio 

 writers, as'AcKERMANN, REIL and BICHAT, thought that the abdo- 

 minal cord of Insects might be compared with the nervus sympa- j 

 thicus of vertebrate animals ; CUVIER and GALL, on the contrary- 

 have disowned and rejected this correspondence. It is necessary h 

 this inquiry to determine in the first place what character is to b( 

 considered of sufficient value to distinguish the spinal cord from thi i 



1 NEWPORT made experiments on lulus, Lithobius and caterpillars of butterflies 

 See Phil. Trans. 1844, p. 283. In Pkasma sometimes one foot is less than the real 

 being a new growth. I found this once also in Redumus personatus. 



