320 
POPULAR SCIENCE REVIEW. 
greatly from ordinary adipose tissue (fig. 2). Numerous 
nerves are seen passing from the ventral ganglia over the fatty 
bodies, which are distributed to the muscle-bands of the 
several segments, but no nerves are supplied to the fatty 
bodies themselves. 
In the larva the development of these fatty bodies (corps 
graisseux of Treviranus) may be easily followed. They first 
appear along the median line of the back as a mass of trans- 
lucent cells containing large nuclei. The mass is separated 
into parallel rows by thread-like septa, upon which the cells 
appear sessile. As the cells gradually enlarge and fill with 
fatty granules, the connecting filaments appear, upon which 
the cells are strung in festoons. The tissue exhibits a beauti- 
fully delicate microscopic picture (fig. 3). 
Our examination of the true parenchyme of the light- 
organs agrees with that of Professor Kolliker. In fig. 4 is 
seen a portion of the surface layer of pale cells next to the 
skin. They are nucleated, and closely packed together amidst 
a fine stroma of delicate fibres, seen sparsely scattered through 
the mass, which seemed to be nerve fibrils of the kind termed 
gelatinous by Grerman histologists. M. Schultze and Dr. M. 
Budneff have employed hyperosmic acid in the investigation 
of these nerves, on account of the property of this acid in 
rendering nerve fibre distinct by colouring it ; but we can 
only refer to Schultz e^s Archivfur Micro scop ische Anatomie for 
the results obtained by them, as we have not had any oppor- 
tunity of making ourselves acquainted with their labours. 
Our figure also represents tracheal trunks, whose branches, 
quickly subdividing, disappear in the substance of the organ. 
The tracheal distribution is exceedingly minute, and may be 
best seen when the parenchyma cells are removed, or when 
the organ is wasted and atrophied in the exhausted insect ; 
the smallest particle of parenchyma contains one or more 
tracheal terminations. In fig. 5, cells and tracheae are seen. 
Both figures are drawn from thin sections magnified 360 
linear diameters, and the tracheal trunks are cut across in the 
preparation of the sections. 
The existence of fine tracheal ramifications in the light- 
organ has been particularly emphasized by Professor Morren, 
who concludes from his investigation that the luminous effect 
is dependent upon a process of respiration (oxidation ? ). The 
direct communication of the principal tracheae with spiracles 
situated on either side of the ventral surface of each abdominal 
segment may be easily traced. Morren observed that when 
the spiracles are closed, the light is immediately extinguished, 
and considers that the opening and closing of the spiracle 
explains the nature and extent of control exercised by the 
