DEVELOPMENT OP PERIPATUS NOViE-ZEALANDI^. 239 



as follows : — The egg is bounded externally by the vitelline 

 membrane {v. m.) ; beneath this and closely applied to it is a 

 peripheral layer of yolk {p. y.), in which are present a number 

 of small round, highly refractive bodies, which stain very deep 

 red with picrocarmine. Within this peripheral yolk layer and 

 forming a ring round the egg is a thin layer of protoplasm 

 {Ec), with clearly defined inner and outer boundaries, and a 

 single layer of nuclei arranged regularly in it. At one point 

 there is a great proliferation of nuclei forming a conspicuous 

 mass [p. n.) on the outer side of the protoplasmic ring; its 

 boundaries are not very sharply defined, so that it passes at its 

 edge into the yolk without any clear line of demarcation 

 separating the two. The space inside the ring of protoplasm 

 is filled with yolk. 



In passing through the series of sections from the middle 

 one just described towards one end of the egg, the proliferating 

 mass of nuclei is found to gradually thin out, and finally dis- 

 appear, so that, as is shown in fig. 15 rf, the protoplasmic 

 band {Ec.) comes to be of the same thickness along its whole 

 circumference. At the same time the diameter of the ring 

 gradually diminishes, and it finally ends not far from the 

 extremity of the egg as a cul-de-sac, the blind end of which is 

 enveloped in the peripheral yolk. 



Passing from the central section towards the other end of 

 the egg, the proliferating mass of nuclei increases in size, and 

 then becomes divided into two masses (vide fig. 15 6, p. n.). 

 These masses are not completely separated from one another, 

 but are connected above and below by a layer of protoplasm, 

 in which nuclei are present, so that a second cavity is produced 

 (fig. \6b,p.) lying below that enclosed by the protoplasmic 

 ring, and bounded laterally by the proliferating mass of nuclei, 

 and above {Sep.) and below by the bands of protoplasm which 

 connect these together. Near the extremity of the egg both 

 these cavities end blindly, the secondary one, i. e. that which 

 lies between the proliferating masses, ending a little before the 

 original cavity. The blind end of the latter is enclosed in the 

 peripheral yolk, which at this end of the eggs shows signs of 



