42 RICHAHD EVANS. 



I. Intkoduction, 



So mucli good work lias been already done on the develop- 

 ment of the PeripatidcB that it is necessary to justify the 

 publication of another account. However, it is not difficult 

 to do so, for not only is the development of the Malayan 

 species still unknown, but even their very existence has been 

 recently doubted. Their close anatomical relation to the neo- 

 tropical forms renders an account of their development doubly 

 interesting and highly desirable. For these reasons it is 

 proposed to give a fairly complete account, and to pay special 

 attention to those points which, hitherto, have not been suffi- 

 ciently elucidated, and are still in dispute. It is not possible 

 to give an account of the segmentation stages, owing to the 

 material not being sufficiently well preserved. The ova being- 

 full of yolk, the younger stages in the development must be 

 taken out of the uteri to preserve them properly; and even 

 when this precaution has been taken, owing to the presence 

 of a thick egg-shell, it will be difficult to ensure good preser- 

 vation. 



II. The Ovum. 



When the germinal cells first appear in the splanchnic wall 

 of the somites, they possess a highly granular nucleus, 

 without a nucleolus, and their cytoplasm is in no way different 

 from that of the remaining cells of the somite. 



When the period of growth of the ovarian ovum commences 

 the nucleus enlarges, its chromatic granules become, relatively 

 to its size, less numerous, and are connected together through 

 the intermediation of fine threads, which take up the chromatic 

 stains. The nucleolus first appears, during the early stages 

 in the period of growth, as a small spherical body. At first 

 it presents no visible structure, but it soon becomes alveolar 

 (PI. 8, 6g. 18a). The cytoplasm, which at first resembles that 

 of the surrounding cells, becomes clearly alveolar in character 

 and remarkably uniform in appearance throughout the ovum. 

 When the ovum has reached an intermediate stage in size, 



