Larva of Ghaoborus Crystallinus ( de Geer). 353 
a detailed examination of these it is necessary to dissect out the 
sacs and transfer them in water to a live box. (PL XVIII., fig. 17.) 
The outer covering consists of a snugly fitting gelatinous coat, 
which is studded with nucleated cells. On the dorsal half only 
are embedded a number of dark-coloured pigment spots, each having 
a minute light-coloured centre. These spots are made up of 
granules, small enough to exhibit Brownian movement when 
scattered in water. The spots are somewhat circular in shape, or, 
if congested owing to increased numbers, hexagonal or polygonal, 
giving a reticulated appearance. 
If several larvae are kept in a tank where light and general 
conditions are uniform, the pigmeet spots often vary on each larva 
— one may exhibit a densely packed collection of spots, and another 
a meagre supply, indicating possibly a condition of health ; on 
sickly specimens they are usually very scanty. 
The next conspicuous detail is a wall of closely-packed and 
extremely thin hoops, each shaped like a rubber band, all of which 
are embedded in a transparent tissue. Each hoop has a depth of 
about three times its width. (PI. XVIII., fig. 19.) 
These hoops are chitinous in nature, responding vividly to 
polarized light. As they dissolve out in the body fluid of the 
larva it is improbable they are pure chitin. 
We placed a sac in Flemming’s fluid. In three hours the effect 
of the osmic acid was seen on the fatty contents, which must be 
considerable, as the surrounding water showed a quantity of dense 
black patches ; the fat we believe was dissolved out from the 
hoops, as they very readily buckled under the slighest pressure. 
We refer to them as hoops, as their appearance in the transverse 
sections suggest it rather than a continuous spiral thread. More 
than one section appears as a complete hoop, which would be 
impossible if it was a section of a spiral. (Plate XIX., fig. 23.) 
They are probably invaginations. Around each hoop is bound a 
spiral band or narrow ribbon of tissue with its edges overlapping. 
(Plate XIX., fig. 24.) This bandage adds considerably to their 
strength and prevents them snapping under pressure. 
On clearing away the outer gelatinous coat and viewing the 
sac with an immersion objective, the overlapping edges of the 
ribbon of tissue appear as slightly projecting extremely narrow 
collars. With polarized light the appearance is altered to that of 
thin black lines running transversely across the face of each hoop. 
(PI. XVIII., fig. 22.) 
If pressure is applied to a sac when in the live box a fracture 
appears midway between the dorsal and ventral sides ; with con- 
tinuous gradual increase of pressure, the fractures will appear over 
the entire surface, which, under an inch objective, gives the 
impression of a piece of watered silk. (Pl. XVIII., fig. 18.) 
Examined with one-sixth objective it will be observed the 
