106 
Dr. Beale_, on Sarcolemma. 
of the maggot will be confirmed by other observers who 
will adopt the same principles in the preparation of the 
specimens which I have followed. 
The transverse markings upon the sarcolemma alluded to 
in page 103 are caused by the ramifications of the tracheae, 
as shown in figs. 7 and 9. From these branches smaller ones 
pass off, and then a network is formed ; when the muscle is 
firmly contracted the sarcolemma is much shortened, and the 
tracheae which run transversely are seen much more distinctly, 
while the branches which connect them are much less 
evident. 
It therefore follows that the membranous sarcolemma of 
the insect-muscle is composed of very fine air-tubes and nerve- 
fibres imbedded in a transparent material, and it is possible 
that this material itself may result from the alterations which 
occur in the course of the development of the above most im- 
portant structures. In some cases there can be no doubt 
that the vessels and nerve-fibres are simply adherent to the 
sarcolemma, but in the insect-muscle the fine nerve-fibres 
and air-tubes are so incorporated with it as to form a part of 
its substance. The rapidity with which this elaborate sarco- 
lemma is developed is very wonderful, since, in the case of the 
maggot, the entire muscle doubled in size in the course of two 
or three days. I doubt if it would be possible to propose for 
anatomical investigation any subject which would be more 
likely to lead to the discovery of highly interesting facts, or 
to the demonstration of important general principles, than 
a minute investigation of the changes occurring during the 
development of the muscles of the maggot or of the silk- 
worm, or of the muscles of the perfect fly or moth, during the 
pupa stage of existence. Although the investigation is un- 
doubtedly extremely difficult, and the utmost patience is 
required to prosecute a subject apparently so limited, for a 
sufficient period of time to stand a chance of success, it must 
not be forgotten that great principles have been discovered 
and wide generalisations have been arrived at in the course 
of long-sustained inquiries into minute details. 
In this paper I have demonstrated an arrangement of the 
nerve-fibre upon the sarcolemma of insect-muscle which has 
not been described before, and in all probability has not been 
seen by any previous observer. The demonstration of this 
exceedingly delicate structure is due entirely to the mode of 
preparation followed. 
