KUNGL. SV. VET. AKADEMIENS HANDLINGAR BAND 49. NIO 4. 11 



Mac Bride of my views on the development in question. It is, indeed, quite op- 

 posed to my account, as quoted above. Considering his misapprehension of the 

 views I have expressed, I ara unable to understand how it can be possible that he 

 should approve them. Referring to the above quotation, or better still, to my paper 

 of 1902, every reader will understand that I never intended anything snch as Mac 

 Bride would impute to me. For I wrote: >The hydrocoele, being almost in contact 

 with the pentagonal floor of the amniotic cavity, has become transformed into a 

 hollovv ring open posteriorly . . . » . 



Thus I have expressly accentuated that the hydrocoele of Parechi?ius miliaris, 

 like that of other Echinoderms, at first takes the aspect of an open hoop. Besides, 

 the examination of the adjoined illustrations in the text of this paper reveals the 

 fact that the open hoop does not become closed posteriorly until that the primary 

 tubes have attained a considerable growth. 



Mac Bride's last paper induced me to undertake a fresh investigation into the 

 matter and I made a complete series of transverse sections of very young pluteus. 

 The elever artist, Mr Georg Liljevall, has drawn them under a high magnifying 

 power and with the aid of an Abbe's camera, and the same artist has also made 

 the figure in the text reconstrueted from these sections. The figured sections confirm 

 my former views in a striking manner. 



The reconstrueted figure 1 represents an exact view of the hydrocoele in a very 

 early stadium and indicates, moreover, how the sections are made. Every other 

 section has been drawn on an enlarged scale. Thus, the figs 72 — 87 represent a 

 series of sections which indisputably prove that the hydrocoele has taken the appea- 

 rance of a hoop or ring, open posteriorly. On fig. 72 the section has cut through 

 the two blind ends of the hoop (h), and the 87 th section presents the curved upper 

 wall of the hoop. Moreover, the reconstrueted figure exhibits also the fact that the 

 five primary tube-feet are in a state of development before the originally open hoop 

 has been closed posteriorly. 



Finally, I desire to express my opinion with regard to the right hydrocoele of 

 Bury and Mac Bride. In 1903 the latter wrotes (p. 297): »Btjry's two papers are 

 the only Communications in which the transverse division of the coelomic sacs into 

 anterior and posterior halves is described. This indication of metamerism in the 

 lar va has been generally received with scepticism. Tiiéel remarks that he was unable 

 to confirm it, and Spengel rejects it.» 



A revision of new sections of young pluteus (fig. 1 in the text, v) reveals the 

 fact that a very inconsiderable vesiele can be discerned close to the ampulla of the 

 stone-canal and on its right side. This vesiele is probably identical with Mac Bri- 

 de^ right hydrocoele or madreporic vesiele. Considering that I have never been able 

 to detect any traces of a right anterior coelom, the origin of this vesiele seems to 

 call for a revision. 



