62 



On the Muscular Nerves of Tipula. 



[June 20, 



where the nerve on approaching the muscular sheath expands into a 

 fan shape, and with its fine granular and nucleated contents embraces 

 the muscle in form of the letter A, without any evidence of the granu- 

 lar matter and sarcous elements being in absokite contact ; the other, 

 called the "stapiform" or stirrup-shaped. The latter, in its early 

 stage, is knobbed in appearance. This, the early stage, is shown gra- 

 dually passing into the cellular, looped, or stirrup form, embracing the 

 fine muscular structure somewhat obliquely, or passing entirely round it, 

 and projecting beyond its edge. In this form also there was no evidence 

 of any union of the granular contents with the sarcous elements, 

 though firm union existed between their sheaths or outer membranes. 

 Eine networks, ending apparently in a granular irregular spot with a 

 pale centre and uniting, are pointed out. The relation and union 

 of short muscles passing between others, and nerve-fibres lying along- 

 side them, with flabelliform expansions, are remarked on, and shovm 

 in the figures and photographs. 



Muscles undergoing degeneration, or the metamorphic change, are 

 noticed, and in no instance could a nerve-fibre be seen attached to 

 them, or a fibre that could with certainty be traced to any nerve or 

 ganglion. No change was ob§erved of a definite character, as regards 

 the mode of union, under muscular contraction. Some of the finest 

 muscular fibres are passed by for special reasons, as constant motion 

 &c. Attention is called to the blood-corpuscles, or to corpuscles which, 

 for convenience, are called creeping corpuscles, and several- figures 

 given. The peculiarities of these bodies are regarded as of consi- 

 derable importance, and, coupled with a remark in Dr. Beale's contri- 

 bution to the Transactions of the Eoyal Society, read May 21st, 1863, 

 in reference to the movement of all forms of living matter. 



A figure is given of the head of the larva, with the pharyngeal por- 

 tion of the digestive tract exserted, which was kept alive for many 

 days ; also of the beautiful buccal plexus regarded as nervous, though not 

 traced from its source. Attention is directed to the difi'erence in the 

 condition of the larva when this portion is exserted by compression, 

 causing death. 



The dif&culties attending this double method of delineation arising 

 from muscular contraction, from the movements of the dorsal vessel, and 

 the digestive tube, and from the thickness of the tissues within and be- 

 yond the true focus, rendered almost hopeless the efibrts to attain exact- 

 ness between the drawings and the photographs, or the rendering by 

 sunlight alone of the minutest points, especially with high pov/ers ; still 

 the photographs are associated to give a truthfulness to the figures by 

 hand. 



The terminations of some nerves in the blood-red larva of another gnat, 

 showing the distinct flabelliform arrangement, are also briefly alluded 

 to, with figures to sustain the views advanced. 



