K. MITSUKURI. 



until in fully grown individuals, there are found nothing but small 

 perforated plates, representing only a small central part of the 

 basai disc and without any trace of the spire. These are moreover 

 comparatively but thinly scattered in the skin. 

 As the changes outlined above take place only by degrees, it is not 

 of course possible to fix any well marked stages ; nevertheless as a matter 

 of convenience in describing and identifying various steps in the changes, 

 I have ventured to assort individuals in various stages of growth into 

 five groups as follows : — ■ 



Stage I: — Includes the youngest individuals whose calcareous bod- 

 ies are all well formed tables. The preparations* made from specimens 



Fig. 2. 



respectively 10, 18, 23, 27 and 30mm. long t present a striking appear- 

 ance. The skin is so thickly crowded with tables that very little space is 

 left between them. These tables (fig. 2) have all a well formed basal 

 disc and a tall slender spire, and are tolerably uniform in size, com- 

 pared with those found in later stages. The commonest size of the basal 

 disc is about 0.06 mm. but exceptionally large ones may reach 0.11— 

 or even 0.12 mm. when measured along the longer axis of those that 



* Made by simply passing a piece of the thin and almost transparent skin through 

 different grades of alcohol, clarifying it in clove-oil and then mounting it in balsam, 

 without any treatment with potash. 



t All measurements made in alcoholic specimens, unless otherwise specified. 



