1864. | : Microscopy. 485 
Diatoms.” Indeed the deposit in the Barbadoes, from which most of 
his new species are derived, seems to be inexhaustible. Like similar 
deposits in the island of Mull, in Sweden, and the coast of Africa, 
the “ Barbadoes earth” is composed of little else but the skeletons of 
these most beautiful and elegant plants. The abundance of species in 
a single locality is indeed very remarkable, for here is a truly fossil 
deposit, richer already in some extensive genera than any other known 
locality, while various genera of singular structure appear to be alto- 
gether peculiar to it. Forty-four species were detected some short time 
since in an examination of the water of the river Thames, as supplied 
to London by the various water companies, but here we have a variety 
of species which far exceed that number. The new species described 
by Dr. Greville belong to the genera, Hupodiscus, Aulacodiscus, Auliscus, 
Biddulphia, Triceratium, and Entogonia, Microscopists and natural- 
ists generally are much indebted to Dr. Greville for the persevering 
manner in which he pursues his researches on this subject. 
On the 8th of June a most valuable and important paper on “'The 
Structure of the Sarcolemma of the Muscular Fibres of Insects, and on 
the Exact Relation of the Nerves and Trachee to the Contractile 'Tis- 
sue,” was communicated by Dr. Lionel 8. Beale, F.R.S., physician to 
King’s College Hospital, and Professor of Physiology and General and 
Morbid Anatomy, in King’s College, London. This paper contained 
new observations by the author relating to the mode of distribution of 
nerves to voluntary muscles. It is a continuation of his researches 
upon this subject, published in the ‘ Philosophical Transactions’ for 
the years 1860, 1862, and 1863, and in the ‘Archives of Medicine,’ 
vols. ii. and iy. In the present communication he showed that the air- 
tubes or trachez ramified very finely over every part of the sarcolemma, 
anastomosing with one another, so as to form a network, the meshes of 
which were a little wider than the strize of the muscle. The nerve 
fibres divided until very delicate ultimate branches, less than +,4,,th 
of an inch in diameter, resulted ; but each of these consisted of a great 
number of individual fibres. 'These branches appear to become lost upon 
the surface of the sarcolemma ; but by examining specimens preserved in 
strong glycerin, and in which the contractile tissue had been ruptured 
at the moment of death within the tube of the sarcolemma, the bundle 
of nerve fibres was seen to break up into a plexus of extremely minute 
fibres, from which branches passed and ramified in the form of a net- 
work, or secondary plexus over every part of the sarcolemma. The 
appearances demonstrated in the author’s specimens were utterly 
incompatible with the notion entertained by certain continental physi- 
ologists, that the nerve terminated by free ends upon the surface of 
the sarcolemma, or by blending with this structure; and also with 
the doctrine that the nerve perforates the sarcolemma and comes into 
actual contact with the muscular tissue. 
The observations were made upon the common maggot or larva of 
the meat fly with the aid of powers varying from 1,000 to 2,500 
linear. 
The general conclusion is, that as in vertebrate animals, the nerve 
forms a network or plexus, which ramifies over every part of the 
