94 



modified outer wall of the bunch of \- o u n g e s t appendages, and contains 

 interiorly an apjjaratus identical to the airfunnel or p n e u m a t o c h o n e of 

 Physonecta. The ordo Auronectae as such has therefore no right of existence; 

 its genera are to be considered as members of a family, Fewkes' Angelidac 

 and the latter belongs again to the order Physonecta. 



In nearly all textbooks of Invertebrate Zoology Auronectae are figured and described as 

 a most remarkable order of SipJionophora. It will be seen how their imiiortance has diminished 

 as a result of our examination of the Siboga material. 



A reconstruction of Archangelopsis is given on PI. XVII, fig. 124. It is of course 

 diagrammatic but constructed absolutely after the facts observed in the sections. 



We have used different colours for the different layers : for the ectoderm we used the 

 yellow colour, for the entoderm grey, for the intermediate layer, the hyaline cartilaginous fulcrum 

 (the German "Stutzlamelle") black, for the secondary ectoderm ("secundares Ectoderm" Chun) 

 green and finally for the chitinous substance of the pneumatocyst black again. 



It will now be seen that also in sections, no trace of an aurophore is to be found, that 

 the bunch of appendages is situated on the same side as part of the pneumatophore. This part 

 of the pneumatophore we consider as the proximal invaginated part (PI. X\'II, fig. 124/^.) 

 the air-funnel ("Lufttrichter" Chun)'). 



The voluminous distal jjart is the pneumatosaccus ("Luftsack") (PI. XVII, fig. i 24/. .car^.). 



Beginning from the lower part of the corm [a. s.) the ectoderm, being the most external 

 layer, can be easily followed on the external side of the mature appendages (PI. XVII, fig. i 24 «..<-.). 

 Going up to the left the ectoderm is traced also along the outer wall of the bunch of young 

 appendages {fi.a.), which as we firmly believe, constitute together the zone of proliferation 

 ("Knospungszone"). The outer wall of the pneumatophore is only a continuation of this same 

 layer (pigment being profusely developed) and the ectoderm joins the outer wall again of the 

 mature appendages on the basal part. 



The course of the fulcrum or supporting layer is absolutely the same (PI. XVII, fig. i 24/.0.). 

 We will speak later of the communication by means of transverse septa (PI. XVII, fig. 124 s.a. a.) 

 which are found to exist between this supporting layer and the same in the air-funnel; transverse 

 septa (.v.a.j^.) are also frequently found between the fulcrum of the pneumatocodon ("Luftschirm") 

 and the fulcrum of the jjneumatosaccus ("Luftsack") on the apical part of the pneumatophore. 



l) In the adult structure one might he inclined to consider the pne'.:niatosaccus as situated prosimally to the more distally 

 placed pneumatochone. When, however, \vc take into account that the pneumatochone is originally the invaginated apex of the pneuma- 

 tocodon, our interpretation above given will appear to be justified. 



Once and for all we should like to institute the following nomenclature of the different parts composing together the pneuma- 

 tophore. Since Haeckei.'s Report of the Challenger expedition they have often been wrongly applied. 



The "pneumatophore" (Luftblase) consists of an outer wall "pneumatocodon" (Luftschirm), an invaginated interior sac, the 

 "pneumatosaccus" (Luftsack), which is often divided into two sacs; the distal one retains the original name pneumatosaccus, the proximal 

 one is called "pneumatochone" (air-funnel, infundibulum, l.ufttrichter). The latter contains the so-called "secondary ectoderm" (pneumadenia 

 Hakckei., Gasdrilse Ciu'n), which should be considered as the remnants of an early extensive development of the original ectodermlayer 

 of the yet undivided pneumato-saccus at its proximal part. 



This ectodermlayer (as has been proved by Professor R. Woltereck in Agaliiia Sarsii 1905) develops in early stages a chitinous 

 substance which later on constitutes the "pneumatocyst" (Luftflasche) of the pneumatophore. The pneumatocodon in the fully develope(? 

 ))neumalophore therefore consists of three layers: ectoderm, chitinous layer, entoderm; the pneumatosaccus of the same three layers but ir 

 inverted succession, the entoderm of the latter facing the entoderm of the former. The pneumatocyst consists only- of one chitinous layer. 



