MYRIAPODA. 



55T 



is thrown off" that the new segments become 

 elongated, and the Julus then appears suddenly 

 to have acquired six new divisions to its body. 

 The production of new legs is equally cu- 

 rious. Up to the present period the animal 

 has but six legs (jig. 322, b a), but four addi- 

 tional pairs are nevertheless in the course of 

 formation. These at present exist only as eight 

 minute nipple-shaped prominences on the under 

 surface of the sixth and seventh segments (b c), 

 four on each, covered by the common tegu- 

 ment, which, we have seen, is becoming deci- 

 duous. The three single pairs of legs that now 

 exist as the only locomotive organs are attached, 

 one pair to the prothorax or second segment, 

 one to the third and one to the fifth segment. 

 The fourth, or segment intermediate between 

 these last, never possesses any legs, but in the 

 female contains the outlets of the organs of ge- 

 neration. The general appearance of the ani- 

 mal has now become less delicate, the head has 

 acquired a darker colour, and a faint broad 

 patch (fig. 322, p) is now making its appear- 

 part of the seventh seg- 



Fig. 322. 



of the 

 bursting 



ance at the anterior 

 ment. This patch, 

 which is permanent 

 through all the ear- 

 lier changes of the 

 animal, is of the 

 greatest utility in de- 

 termining the pro- 

 duction of new seg- 

 ments. It is in 

 the segment imme- 

 diately posterior to 

 this that the male 

 organs find their out- 

 let, a circumstance 

 the more remarkable 

 from the fact that 

 this outlet is in the anterior part 

 original germinal space, and at the 

 of the egg this is very near the termination 

 of the body. Such was the condition of 

 the young Julus one hour after leaving the 

 amnion. It soon began to exhibit its animal 

 powers, to shew the instincts peculiar to its 

 species, and to be sensibly affected by ex- 

 ternal causes. In less than six hours from the 

 bursting of the amnion the little creatures were 

 in motion. At first the antennae were the or- 

 gans employed. They were moved slowly to 

 and fro, and seemed to gain power by use. 

 In a short time the limbs began to be extended, 

 and the animal slowly raised itself upon them 

 for the first time. Its first efforts at locomotion 

 were exceedingly feeble, but it gradually gained 

 strength. At the end of twelve hours the em- 

 bryos crawled slowly about, but moving the an- 

 tennae briskly. On exposing them to a strong 

 light a marked effect was produced in their 

 movements. They evidently were greatly af- 

 fected by it, and seemed instinctively to shun 

 it. This was the first marked exhibition of 

 instinct. Locomotion was at first performed 

 very slowly but with instinctive care. The 

 anal segment, previously to each step, was 

 expanded like the anal leg of the larva of an 

 insect, and being first attached like a true pro- 



leg, and its step, as it were, measured, its body 

 was carried forwards by an effort that extended, 

 as in insects, from segment to segment. 



At twenty-four hours after escaping from 

 the amnion the young animals were lying toge- 

 ther in a heap, but when disturbed seemed to 

 have acquired more power of moving : they 

 remained quiet except when aroused, and had 

 not yet taken food. The only marked diffe- 

 rence in their appearance, excepting that they 

 had still further increased in size, was in the 

 nipple-shaped protuberances on the sixth and 

 seventh segments, the rudiments of future legs. 

 These were now more distinct and mammiform. 

 Ten hours later in the day they assumed still 

 more the appearance of nipples projecting from 

 the under surface of the segments. When 

 examined in specimens that had been placed in 

 spirits of wine, it became evident that these 

 projections were occasioned by the develope- 

 ment under the deciduous tegument of four 

 new, but exceedingly minute legs, complete in 

 all their parts, each covered by its proper skin. 

 The claws to the legs of the other segments 

 were also more strongly marked. The new 

 segments ff) were more developed, although 

 still covered by the common tegument, and, as 

 in the preceding state, forming only one divi- 

 sion of the body, while a small space behind 

 them indicated the point from which other new 

 segments were to be produced. 



On the nineteenth day, Mr. Newport found 

 that the animals had acquired a little darker 

 colour, but were still remaining quiet in their 

 cells, and did not appear to have taken food. 

 The enlargement of the body had not extended 

 to \heprotkorax, which did not increase in size 

 in proportion to the rest. The double pairs of 

 new legs to the sixth and seventh segments 

 were now distinctly visible through the exter- 

 nal tegument, which had begun to be separated 

 from the under surface of the old segments, to 

 which up to this period it had closely adhered. 

 The patch on the side of the seventh segment 

 had become darker, and the new segments 

 were further advanced. 



On the twenty-first day (Jig. 323) the young 

 Juli still remained coiled up and perfectly 

 Fi 323 quiescent, with their 



legs disposed side by 

 side along the under 

 surface of the body, like 

 the pupae of Lepi- 

 dopterous Insects. The 

 new legs had consider- 

 ably increased in size, 

 as well as the whole 

 animal, although it had 

 not taken food. The ani- 

 mal was still partially 

 coiled up, but the skin 

 that covered its body 

 was greatly distended, 

 more especially along 

 the ventral surface. It 

 was less able to move 

 than before, the period 

 of throwing off this skin being fast approach- 

 ing : the double legs of the sixth and seventh 



