AND THE DEVELOPMENT OF THE MYRIAPODA. 
121 
prolongation of which segment in some larvae of insects, the Sphingidce*, &c., may 
be regarded, as in the lulus, as the remnant and representative of the funis. 
This embryo condition of the animal will thus explain the circumstance of its 
first acquiring a slight power of locomotion, and then remaining perfectly quiescent, 
without taking food, to prepare for this change, — the third period of its embryo life. 
It is then to prepare for this last change that it now lies perfectly quiet, absolute rest 
being necessary to its proper evolution, which may probably be retarded by the 
slightest disturbance. 
The lower portion of the alimentary canal is now distinctly visible through the new 
segments. When examined by transmitted light, it exhibits a corrugated or folded 
appearance, being folded to allow of its sudden extension at the period of throwing off 
the skin, and elongation of the segments. The colon is of a very dark colour, and ex- 
hibits its thickened peculiar structure, with its longitudinal muscular bands. Around 
its posterior part I observed an aggregation of what appeared to be globular cells. 
They seemed to be part of the organs of generation in the course of development. At 
first I regarded them as hepatic vessels, but this could hardly be the case, from the fact 
that each of these organs directly enters the canal as a straight vessel ; but they might 
be vessels folded up to be unfolded suddenly, as in the case of the alimentary canal. 
On the twenty -second day (fig. 15 .) but little further advance is made in the deve- 
lopment of the animal, save only that the original segments more distinctly exhibit 
the appearance of the segments of the perfect Myriapod. This appearance was more 
distinct than on the previous day, and consisted of transverse markings that divided 
each segment into two parts, the posterior of which was now impressed with longitu- 
dinal striae. From the length of the posterior portion of each segment being slightly 
shorter than the anterior, it is evident that the segments had not yet acquired their 
fullest development, although they were more advanced than on the previous day. 
The dark patch of colour on the sides of the seventh segment, which first began to 
show itself on the seventeenth day, was now much more distinct, and became each 
day more and more apparent. The head of the animal was a little more bent on the 
thorax ; the limbs more straightened ; the new segments much further developed ; 
and the whole indicated that the deciduation of the covering was now rapidly ap- 
proaching. 
The fourth period of development is as distinctly marked as the third. The young 
lulus now has seven pairs of legs, and fifteen segments to its body. 
On the twenty-sixth day (fig. 16 .) nearly the whole of my specimens had changed 
their condition. In the morning some of them had already undergone the change, 
and were now briskly moving their antennae, but still remained collected together. 
The antennae were elongated at least one-third of their original length, and exhibited 
six distinct joints. The eye still consisted of a single ocellus, but this was now sur- 
rounded by a darker coloured portion of the tegument. The new legs ( b , c) were 
* Philosophical Transactions, 1834, Part II. Plate XIV. figs. 11 and 12. (12.) 
