114 MR. NEWPORT ON THE ORGANS OF REPRODUCTION, 



rudimentary state. Posteriorly to the fifth segment, the body is more soft and deli- 

 cate, and the segments less clearly defined. This results from the circumstance that 

 it is at this part of the body that the future new segments are to be produced. 



On the fourth day (fig. 7-) I first observed 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 rudiments of its future legs had become larger and more obtuse (6. a) ; 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 posterior part of the body, and the funis {d) 

 was contracted, as if about to separate. Internally, the body was still formed of cells 

 aggregated together, 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 sur- 

 rounded on all sides, was the newly-formed alimentary canal. The canal was now 

 more opake, and when pressed out of the body, more firmly adhered together, than 

 any other internal structure, and was distinctly 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 indistinct. I could observe no 

 perfect fibre. This fact will sufficiently account 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. We have seen that on the third day 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 {f), that connects the seventh with the eighth 

 segment, at the posterior margin of which the funis {d) enters, and which segment is 

 permanent as the penultimate throughout the life of the animal, that the formation 

 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 similar structures. 



On the ninth day (fig. 8.) the changes have advanced much further. Not only 

 have the future new segments become more distinct (/), but transverse depressions 

 are also seen on the dorsal surface of the original segments, showing their division into 

 double ones, as in the perfect animal. The rudiments of the legs are now further 

 developed (6. a), and their transparent distal extremities are seen through the invest- 

 ing membrane applied closely together, and extended along the ventral surface of the 

 body, as in the nymphs or pupse of true insects. The antennae and ocelli are more 

 apparent, and the embryo itself has increased at least one-third of its original dimen- 

 sions. It is still attached by the funis to the shell ; but this attachment is daily be- 

 coming more fragile, and is now separated by very slight causes. The embryo has 

 thus continued to grow through nine succeeding days, since the bursting of its shell, 

 without any visible means of nourishment, the nutriment supplied by the yelk having 



