220 



W'liilo it would lliiis ;i|)|)(.';ir to be a riilo Huil Ihe lai\';v of llu' I'Ikiiuto- 

 /unia have no Hrachiolaria-slaf^e, the lads known of the (lt'V(.'lo|)nu'nl of 

 Ihc Spinnlosa and the Forcii)ulala (Cryptozonia) seem lo indicate llial their 

 larva- aic clKiraclcrislic through having a Brachiolaria-stage'). The dif- 

 ferences between the various types of Brachiolarias are very unessential, 

 consisting mainly in the median Rrachiolarian process being now round, 

 with a crown of pa]n]l;e. now Hal with a series of papilhe along the edges; 

 this need not be considered here. The point to be emphasized is that the 

 Brachiolaria-stage is knt)wn lo occur only in the more spec- 

 ialized Starfishes, and the Hrachiola ria-arms and the suck- 

 ing disk connected therewith are therefore later acquired, 

 specialized structures. Accordingly Ihe homology generally 

 snj)posed to exist between the sucking disk of the Hrachio- 

 laria and the I'elmatozoa n slalk is only apparent, and Ihe 

 greal pari il has [)layed in phylogenetic speculations is un- 

 just ificd, not being supported by facts acquired from an extended study 

 of the development of Asteroids. Of course, 1 agree that very much more 

 knowledge is needed for finally establishing this statement as a fact beyond 

 disf)ule. The metamorphosis of the .l.s/ropcr/c/}- and Luidid-huxiV need 

 being studied in a much more detailed way than has hitherto been done, 

 it would also be of the greatest interest to study the development of such 

 Aslropeclinids and other Phanerozonia as have large, yolky eggs and lo 

 see whether the larv;e of such forms possibly develop Brachiolarian j)ro- 

 cesses and a sucking disk, as do e. g. the .S'o/^/.s7r/-larva\ If my views on 

 the development of Asteroids are correct, Ihey should not develop such 

 processes, or, at least, no sucking disk. (Processes might not necessarily 

 be homologous with the Brachiolarian arms). Anyhow, the facts hitherto 

 known of Asteroid development seem to nie to enforce the above conclu- 

 sions. 



It is of importance to notice the fact that during the metamorphosis of 



') II llio larvii lii^iin-(l on p. I I'.t ol iii.\ papiT "Noli's on llu' dcvflopiiu'iil ami llu' lar\al 

 fonus of some Scandinavian liciiinoilernis" really l)eloiiKs to Slirhastir roxeiis as supposed 

 Ijy me ttiere, tiial will be an exception to the rule indicated by the direct observations on 

 the development of the said groups of starfishes. 1 would not be inclined to think this prob- 

 able and Iherefore now doubt the correctness of that suggestion, 'liie larva figured would 

 then belong to Aslnipicitn irreyitlarif:. 



Gem mi 11 in his paper on "The larva of the Starfish of I'orania pulvillus (O. F. M.) (Qu. .1. 

 Micr. Sc. Vol. 61. lOl.'i) concludes from the fact that he has found this larva to have a Brachio- 

 laria-stage that "it is evident that the division of Asterids into Phanerozonia and Cryptozonia 

 is not necessarily associated with fundanuiital dilTereiices of developiucnl." .\s. however, 

 the position of the family (lymnasleridic (or Asteropid;e). to which I'urania belongs, within 

 tlie I'hanero/onia is doubtful, this conclusion may not be justilicd. The fact of the Porania- 

 larva being a lirachiolaria at most may serve to prove that this larval stage makes its appear- 

 ance in tlie most specialized group of the Phanerozonia. 



