20 
SUMMAKY OF CURllENT RESEARCHES RELATING TO 
faultlessly printed, index to the first ten volumes of his ‘ Zoologischer 
Anzeiger.’ This volume will be of great service not only to the 
possessors of these volumes, but to all students of zoology, for it is a 
guide to the literature of the science during an important decade. 
Zoology of Mergui Archipelago. — The descriptions of the collections 
made by Dr. John Anderson in the Mergui Archipelago are now com- 
plete ; their publication has extended over three years, and they occupy 
volumes xxi. and xxii. of the Journal of the Linnean Society. 
B. INVERTEBRATA. 
Medullated Nerve-fibres and Neurochord in Crustacea and Anne- 
lids.* — Herr B. Friedlaender has made a special examination of the 
neurochord of Mastobranclius ; he finds that its sheath consists at least 
largely of a substance which is very like the medulla of vertebrate 
nerve-fibres. Within the neurochord there is a substance which is 
coagulated by alcohol, sublimate, heating and so on, which appears to 
be of a plasmatic nature, but does not seem to have any definite structure. 
This substance is the direct continuation of the processes of the neuro- 
chord-cells, and appears to agree with them completely. 
The neurochords of Mastobranchus are three in number, are tubular 
in form and divisible into sheath and contents ; the former consists 
largely of (in Pertik’s nomenclature) myelinogenous or nerve-medulla- 
like substance ; it is probable that there is also a supporting substance, 
but this cannot be definitely affirmed. 
A comparison of a number of apparently similar structures seems to, 
show that the so-called neurochords of Mastobranchus, Lumbricus, and 
probably of other Annelids, the nerve-tubes of Palsemon, Squilla, and 
very probably of other Crustacea and perhaps of Arthropods in general, 
and the medullated fibres of Vertebrates are, fundamentally, the same 
structures. They are all tubular and consist of wall and conteuts ; 
when the former is of considerable thickness it appears in optical 
section to have a double contour. The wall of these tubes appears in 
many (? all) cases to consist at least partially of myelinogenous sub- 
stances which exhibit certain differences in some cases. Many authors 
liave erroneously regarded the “ myelin formations ” to which they give 
rise as part of the contents of the tubes. The contents of the tubes 
is a protoplasmic substance, rich in water, and directly continuous with 
the processes of the ganglionic tubes. Among Vertebrates these contents 
are called axis-cylinders, a name which may be given a wider and more 
general extension. On the whole, we may conclude that the so-called 
neurochords are medullated nerve-fibres, and deny the truth of the general 
proposition that medullated nerve-fibres are found in Vertebrates only. 
In conclusion, the author considers the function of the neurochords ; 
he is inclined to doubt that of their being an organ of support. With 
some diffidence he is inclined to associate them with the power possessed 
by a number of Annelids and Crustacea of making sudden contractions 
of the body ; in such movements there is an almost simultaneous con- 
traction of the homodynamous muscles of all or nearly all the segments 
of the body. 
MT. Zool. Stat. Neapcl, ix. (1889) pp. 205-65 (1 pL). 
