OF THE LARVA OF CORETHRA PLUM1CORNIS. 73 



from the surface. No longitudinal fibrillation seems to take place 

 in them till a very late stage of their growth, when it occurs by a 

 splitting up of the bundles at the points of their attachment, and 

 then the bundle or band becomes a fasciculus of fibres, but long 

 prior to this stage the interesting phenomena of their behaviour 

 under polarized light may be observed, the entire muscle being 

 thrown into contraction by disturbing the larva, transverse bands of 

 colour appear which vary with the intensity of the contraction. The 

 sarcolemma is thrown into corrugations by the contraction, each 

 corrugation showing on one side a colour and on the other side its 

 complimentary tint, and as the contraction ceases, and these corru- 

 gations subside, the colours fade and gradually pass away, remind- 

 ing one of the coruscations of an aurora. Upon treating the larva 

 to a very dilute mixture of spirit, acetic acid, and glycerine, the 

 muscles threw off waves of contraction which, passing down the 

 course of the fasciculus, could be readily watched, the node of con- 

 traction showing a fibrous appearance rather than a striated. 



The union of the nerves with the muscles is shown in a most 

 instructive manner in this larva ; the Doyerian eminences are tri- 

 angular processes of nerve matter, through which the nerve becomes 

 fused with and pierces the sarcolemma of the muscle. Several of 

 these eminences can be seen either in profile or as plates, according 

 to the position in which the larva may place itself. 



The dorsal vessel or heart forms another interesting subject of 

 observation, and will attract the attention of all who examine Core- 

 tlira by its regular pulsation, as well as by the incessant movement 

 of those pale brown bodies attached to its walls. While voluntary 

 muscles are at rest, those organs immediately subservient to life 

 must perform their offices independently of volition, and the animal 

 heart, whether it be of the vertebrate or invertebrate type, must 

 keep up the constant current of the circulating fluid. It may differ 

 in shape between the two classes, but its office is the same, and it 

 is under the same nervous influence, viz., that of the sympathetic 

 system. The ventral chain does not give off any fibres to supply this 

 dorsal vessel ; therefore these incessant pulsations, averaging from 

 12 to 19 per minute, are automatically governed by the pale brown 

 granular bodies attached to its walls. These bodies are of various 

 shades of brown, and carry one or more large nuclei, increasing by 

 self-division. They are exactly of the character of the sympathetic 

 nerve-cells figured in " (Strieker's Histology," p. 176. The dorsal 



