G8 S. HIROTA. 



insufficient to inquire the line neuro-vascular system of, or to study the 

 development of, the comet-sliaped youngs. With my collection we may, 

 however, compare the latter with the normal forms in regard to some 

 internal organs, and it serves also to demonstrate some facts concerning 

 spontaneous breaking of the arms, every piece of which giv^es birth to a 

 ' comet.' 



Fig. 1 and Fig. cj represent the younger and the older 'comet,' respec- 

 tively. The younger 'comet' possesses a principal arm 71 ihdi. long and 

 four small arms, varying from 12 to 14 Dim. in length, while the older 

 bears a principal arm .5-i nini. long and four small arms which vary from 

 14 to 18 mni. in length.* In sections of the generative organ contained in 

 theprincijial arm, the older is ascertained to be a female while the younger 

 is questionable, generative cells being not yet evidently differentiated. All 

 arms of both speciniens possess a normal ambulacral furrow and a normal 

 integument with; papillae, the essential difference between the principal arm 

 and the small arms being only the difference of sizes of corresponding parts. 

 On this aboral face there are in both ' comets' four or five sunken spots at 

 the yery base of the principal arm. They are perhaps remnants of a wound 

 through which the principal arm was dropped. Haeckeh'^ speaks in his 

 paper : " Es scheint, dass zwei dorsale Porenfelder den Ausgangspunct fiir 

 die Bildung der beiden neueo Madreporenplatten liefern." Through dissec- 

 tion it is niade certain that some of these sunken spots near the median line, 

 which were not noticed by Haeckel, have papillae in them while the two — 

 one on each side — nearest to the interbrachial angle form primitive madreporic 

 ]:)lates, on which the stone canals end. in the surface view, these madreporic 

 plates in the process of formation are nothing more than elongated shallow 

 depressions with a granular surface like the surrounding regions, and they 

 have yet no characteristic winding structure, though the latter is recognized 

 in very earl)^ stages in normal forms, or, according to Haeckel, in still older 

 ' comets.' IJy studying the young ' comets ' figured by Haeckel as well as 

 my own speciemens, we notice that the small arms of a ' comet ' are short in 

 proportion to their girth ; indeed the earlier the stage, the broader the 



* The leng-th- of all arms is uieasured ou the Tevteljral ridi>"e. 



