MYRIAPODA. 



555 



the circumstance that it is at this part of the 

 body that the future new segments are to be 

 produced. 



On the fourth day, Mr. Newport first ob- 

 served some faint traces of a single eye, or 

 ocellus, on each side of the head. The embryo 

 had now further increased in size, and the ru- 

 diments of its future legs had become larger 

 and more obtuse, an appearance which the 

 newly-formed limbs of the Articulata often 

 exhibit previously to their further elongation. 

 Traces of the formation of internal organs were 

 now evident through the tegument at the pos- 

 terior part of the body, and the funis was con- 

 tracted as if about to separate. Internally the 

 body was still formed of cells aggregated toge- 

 ther, but differing more in size than at any 

 previous period, as if they were becoming 

 fused into separate tissues, and in the midst 

 of them and closely surrounded on all sides 

 was the newly-formed alimentary canal. The 

 canal was now more opaque, and when pressed 

 out of the body more firmly adhered together 

 than any other internal structure, and was dis- 

 tinctly composed of an aggregation of very 

 minute cells. Around the sides of the body 

 muscular structure was also in the course of 

 development, but as yet was exceedingly in- 

 distinct, insomuch that Mr. Newport could 

 discover no perfect fibre, a fact that sufficiently 

 accounts for the entire absence of spontaneous 

 motion in the embryo up to this period. 



A new process was now about to commence 

 the development of new segments. On the 

 third day, as has been already stated, the pos- 

 terior part of the body is less distinctly divided 

 into segments than the anterior, the first five 

 segments being most distinctly marked. The 

 sixth and seventh are now more defined. It is 

 in the membrane/,^. 321, that connects the 

 seventh with the eighth segment at the posterior 

 margin of which last the funis (d) enters, and 

 which segment is permanent as the penultimate 

 throughout the life of the animal, that the for- 

 mation of new segments is taking place. At 

 this period it is only a little ill-defined space 

 that unites the seventh and eighth segments 

 into one mass, but in proportion as the anterior 

 parts of the body become developed, this part 

 is also enlarged, not as a single structure, but 

 as a multiplication or repetition of separate si- 

 milar structures. 



On the ninth day the changes have advanced 

 much further (fig. 320) ; 

 not only have the future 

 new segments become 

 more distinct, but trans- 

 verse depressions are also 

 seen on the dorsal surface 

 of the original segments, 

 shewingtheirdivision into 

 double ones, as in the 

 perfect animal. The rudi- 

 ments of the legs are now 

 further developed, and 

 their transparent distal 

 extremities are seen through the investing mem- 

 brane applied closely together and extended 

 along the ventral surface of the body, as in the 



Fig. 19. 



nymphs or pupae of true Insects. The an- 

 tennae and ocelli are more apparent, and the 

 embryo itself has increased at least one-third 

 of its original dimensions. It is still attached 

 by the funis to the shell, but this attachment is 

 daily becoming more fragile, and is now sepa- 

 rated by very slight causes. The embryo has 

 thus continued to grow through nine succeed- 

 ing days, since the bursting of its shell, without 

 any visible means of nourishment, the nutri- 

 ment supplied by the yelk having been ex- 

 hausted before that occurrence. Hence it be- 

 comes a matter of inquiry from whence it now 

 derives its means of growth ? Whether it has 

 already sufficient materials derived from the 

 egg, and stored up within itself for its future 

 development, or whether the external inclosing 

 membrane may not still contribute to the func- 

 tion of nutrition by absorbing fluid condensed 

 from the air of the humid locality in which it re- 

 sides. The probability of this last supposition, 

 says Mr. Newport, is somewhat countenanced 

 by the fact that I have constantly observed the 

 membranes of the embryo at this period co- 

 vered with microscopic drops of fluid, but 

 whether this is fluid condensed on the mem- 

 branes from the atmosphere of the dwelling, 

 or whether it results from the transudation of 

 that which was contained in the amnion, re- 

 mains for future inquiry. 



Up to this period the embryo gives not the 

 slightest evidence of spontaneous or voluntary 

 motion. Internally it is still composed of cells 

 of different sizes that are now in the course of 

 producing muscular and other structures. In 

 some parts of its body no arrangement of them 

 seems as yet to have taken place, the cells 

 being merely aggregated together. Cells of 

 three very distinct sizes now exist. The dia- 

 meter of the largest of these is nearly three 

 times that of the second size, and the second 

 again are nearly twice and a half the size of the 

 smallest. The smallest sized cells fill up the 

 interspaces between the others, and appear as 

 if breaking down to form interstitial or cellular 

 substance, while the second sized cells are 

 arranged in rows to form particular structures. 



In the midst of these cells the alimentary 

 canal is now nearly complete, but Mr. Newport 

 was unable to observe its connexion with the 

 funis. At its anal extremity it is a little dilated, 

 and extends forward as a short straight intestine, 

 the rectum, until it arrives at a part where a 

 valve seems about to be formed. The diameter 

 of the canal is there enlarged, and on its surface 

 are three distinct longitudinal muscular bands. 

 The so-called hepatic vessels also exist as dis- 

 tinct tubes inserted one on each side into the 

 alimentary canal at the constricted or valve-like 

 part above noticed. The canal is then conti- 

 nued forwards until it is again dilated into the 

 proper stomach, and terminates or rather com- 

 mences in a narrow oesophagus. It is much 

 longer than the body of the embryo, being con- 

 voluted or folded upon itself in its lower por- 

 tion, to adapt it to the changes that the body 

 undergoes in the enlargement and elongation 

 of its segments. It is not yet separated from 

 the now forming structures by any distinct 



