22 
EMBRYONIC DEVELOPMENT 
them between two glasses proved unsuccessful: the little creatures being constantly 
crushed under the slightest pressure. Hours after hours were spent, the eye over the 
microscope, in order to form a complete idea of their outlines, until I was prepared to 
carve models of their shapes, from which models, figs. 94 — 103 inclusive, were drawn 
by Mr. A. Sonrel. This circumstance is mentioned to account for their artistic ap- 
pearance ; also to explain their being mere shaded outlines, without any attempt for 
exhibiting their structure. As copies, in natural size, of my models, they are propor- 
tionally a little larger than the other figures. 
The body of the larva is semi-transparent, in which no organs are as yet to be dis- 
covered; the eye-specks alone, dark brown, are very conspicuous. VibrillfB still cover 
the whole surface of the body, but are especially developed around the prominences of 
the back and belly. Indeed, when speaking of back, belly and sides, it is in refer- 
ence to the eye specks, which we consider as appertaining to the anterior region, for, 
in their motion, the larvae keep in no permanent position or orientation. Almost any of 
the regions may be directed forwards; it is a perpetual rolling rather than a head- 
wards progression ; no region yet predominates exclusively over the other regions. 
Towards the eve of the larval life, the larvae are no longer moving in open medium. 
They keep nearer the bottom of the vessel, move slower,, but are still subjected to those 
contractions of their body, which alternately and temporarily modify their shape. 
XIII. 
THE CHRYSALIS. 
That larva which was seen so lively, so active, so plastic, so polymorphic, becomes 
a mummy-like body, an immoveable chrysalis (fig. 104), eight or ten days after it first 
began to revolve as an embryo (fig. 52, 53 and 55). 
This chrysalis is an elongated, slightly curved body, semicylindrical in shape, con- 
cave above and flat below, as shown by a transverse section (fig. 105). Opaque at 
both extremities, w T hilst the middle region remains transparent, no organs are discerni- 
ble in any of the regions. The external envelope, or case, is a tough membrane, 
through which the microscope can hardly penetrate. When crushed between two 
glasses, the cellular contents then escape,' leaving the case empty. 
I am not prepared to give any information in relation to the length of time which 
the animal remains in this state, having lost a great number of these little bodies 
which could scarcely be distinguished amongst the sand and organic substances 
always floating in the water; and when the latter had to be changed, many of them 
w T ere unavoidably lost. On this account my investigations, have come to a tempo- 
rary close af this point of their history. 
For a time, I w r as still in doubt as to whether these singular chrysalis-like bodies 
