ON THE CALCAREOUS DEPOSITS OF STICHOPUS JAPONICUS. 39 



the discs that are affected by the " Hernmungsprozess " have all more 

 or less spinous margin and are reduced in size in various degrees. (See 

 Théel, Pl. VIII, Eig. 2d.) When no spire is developed a table be- 

 comes nothing but irregular perforated plates with spinous margin. 

 The larger ones of this kind graduate by degree into small, perforated 

 plates which we saw in the preceding stage. At this period, therefore, 

 we see three kinds of calcareous deposits : (a) completely built tables 

 such as we saw in Stage I, (b) tables showing various degrees of imper- 

 fection and having spinous margin, and (c) perforated plates, mostly with 

 spinous margin which from tolerably large ones shade off into quite 

 small quadriloculate forms. 



The specimens which showed best the characteristics of this stage 

 are several individuals 200-250 mm. long (in fresh state), which I obtained 

 at Kanagawa and which I believe, from a series of observations made at 

 the same locality, to be at the end of their first year. There are, how- 

 ever, others which are smaller (175 mm. fresh. Tokyo market) and larger. 

 Théel's specimens measured 220 mm. and must have been considerably 

 larger in fresh state. 



Stage IV: — This is the stage in which the original specimen de- 

 scribed by Selenka must have belonged, although it was only 110 mm. 

 in length. The tables of the original form which were characteristic of 

 Stage I, have now all disappeared or, if present, very rare, and only those 

 that show various degrees of imperfection are seen and even these are 

 not very numerous. The spire is mostly very low, having generally 

 only one or at the most two transverse beams, and may be reduced in 

 the number of the pillars. Various forms of asymmetry* may be pro- 

 duced by difference in lengths of the pillars on the same disc, or by the 

 pillars inclining towards and fusing with, one another. Selenka's Fig. 

 35 represents without question one of these forms, and I have seen many 

 which are quite near it, although never one which is exactly as symme- 

 trical as the one the figure shows. By far the most prominent feature 



Such forms may also be seen from earlier stages. 



