THE NEW GENEALOGICAL TREE 435 



The question has been widely discussed whether there were 

 at least some temporary traces of a segmentation in the Anlage 

 of the perigastrocoele which develops from a pair of telo- 

 blasts. Hatschek (1881) could find no trace of a segmentation 

 in the embryos oi Sipimcuhis niidtts, Gerould (1906) on the other 

 hand described and depicted from three to four pairs of coelom 

 sacks which he believed to have found in the embryos of 

 Golfingia vulgaris. Gerould has later revoked these facts ; he 

 considered these phenomena later as a consequence of a fold- 

 ing which is due to a strong contraction. Gerould made 

 this statement in a letter only, which is quoted by Hyman. 

 Those who prefer to see in the Sipunculida a preliminary stage 

 of an evolution in the direction towards the Annelida will find 

 the state of things, such as it appears nov\' after Gerould's re- 

 vocation of his findings, as very important and favourable to 

 their interpretation. I, on the other hand, consider that it is 

 much less important whether in fact a segmented state is still 

 recapitulated in the perigastrocoele of some species belonging 

 to the Sipunculida. It is not impossible that during the future 

 researches forms will be discovered among the more than 

 250 species of the Sipunculida, which differ considerably from 

 one another, where such recapitulations will be found preserv- 

 ed. Yet even if no such traces of a segmentation are actually 

 found preserved in any of the recent species, there are still 

 other numerous properties which seem to support my thesis 

 that the Sipunculida evolved as a result of a secondary simpli- 

 fication and of a specialization of their way of life. 



I wish finally to mention here the urns which are so cha- 

 racteristic of the organization of the Sipunculida. The structure 

 and the ontogenetic development of these urns are well 

 enough known. Yet there exists a considerable uncertainty 

 about their function, and even more so of their origin, of their 

 phylogeny. These urns remind me— by the whole line of their 

 development : the freely swimming urns, the attached urns, the 

 coelothelium cells which are strongly covered with cilia; by the 

 fact that they collect material to be excreted; and finally by 



