40 



E. 



MITSUKURI. 



Fig. 3. 



of the calcareous deposits in in- 

 dividuals of this stage is the pre- 

 sence of those which Selenka 

 named " Hemmungsbildungen " 

 (Fig. 3). These show various 

 sizes, but on the whole are small- 

 er than those in the typicus stage. 

 On many are seen little knobs 



Some forms of perforated plates. 



X 300. 



which are the rudiments of the pillars of a spire. 



It is impossible to give any limits in the lengths of individuals 

 which belong to this stage. Those that I placed here range between 

 50 mm. (alcoholic specimen) and •JlOmm. (in fresh state;. Probably still 

 larger ones may be placed here. 



Stage V: — This I propose to call the armata stage, for the speci- 

 men which Selexka named Holotliuria armata, had calcareous bodies 

 which are typical of this stage. In other words, all forms of tables with 

 a spire have now entirely disappeared. At the most, there are only 

 simple knobs which represent the rudiments of the pillars of a spire. 

 All the calcareous bodies are therefore in the shape of perforated plates 

 or Selenka's " Hemmungsbildungen." In the younger ones of this 

 stage, these perforated plates may be still large and have spinous margin, 

 but the older the individual, the smaller and smoother become the cal- 

 careous bodies, and the nearer they approach the shape of a ring with 

 four openings, representing the four central holes in the discs of the earlier 

 tables. In the very oldest, even these four holes are not complete, and 

 a part of the circumference may often be lacking to the ring. The 

 calcareous deposits are also much more sparsely distributed than in 

 earlier stages. 



I need hardly remind the reader that as the above five stages have 

 been artificially marked out in an unbroken series of changes, many an 

 intermediate state of things will be found, which an investigator will 

 find difficult to put precisely in any one of them. I claim for them 

 nothing beyond some advantage that they afford in elucidating the 



