ON THE CALCAREOUS DEPOSITS OF STICHOPUS JAPONICUS. 



41 



the process of changes in the calcareous deposits of Stichopus japonicus. 



It is evident from what has been given above that the calcareous 

 deposits in our species are more complete and show more primitive 

 characters in young stages than in older or adult forms. In the young- 

 est stages examined, they have almost the character of a calcareous coat 

 of armor, similar to that of a starfish or of a sea-urchin. There are un- 

 doubtedly physiological reasons for this : the youngest individuals have a 

 very thin and pliable skin and muscle layer so that some sort of protec- 

 tion and support is a necessity. But a possible phylogenetic signi- 

 ficance should not be lost sight of. 



It will be seen that I agree iwith Theel in regarding Holothuria 

 armata of Selenka to be only a form of Stichopus japonicus. My rea- 

 sons for thinking so are as follows : — I have fortunately some specimens of 

 Holothuria armata which Prof. Selenka kindly identified for us during 

 his stay in Japan. There can be therefore no question as to their being 

 Holothuria armata. Now, an examination of the calcareous deposits of 

 these specimens reveals a condition exactly like the fifth stage of Sticho- 

 pus japonicus. I see no reason for separating them from other speci- 

 mens of Sticìiopìis japonicus of the same stage, so far as the calcareous 

 deposits are concerned. Unfortunately, these specimens lack the viscera, 

 and I have not yet had an opportunity of examining the reproductive 

 organs of this type. But my friend, Mr. Nozawa of the Hokkaido 

 Fisheries Bureau informs me that when he examined some years ago 

 the specimens of that form in order to determine its breeding season, he 

 remembers seeing two genital bundles, one on each side of the median 

 mesentery. There is therefore very little doubt in my own mind that 

 the form which Selenka has signalized as Holothuria urinata is the 

 northern form of Stichopus japonicus. It is easily distinguished by 

 having four rows of many long pointed papillae along the two dorsal 

 ambulacra and the lateral margins, and by having numerous much small- 

 er papillae interspersed between these four rows. This form is found in 

 the Hokkaido (Yesso) and the northernmost part of the Honshu (the 

 main Island of Japan). As we go down southward in our country, the 



