382 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



form occurs in the Schizotarsia), in the lower Entomostraca such as 

 Copepoda and Ostracoda, and in CoUembola and Diplura. Annulated 

 antennae are found in Malacostraca, in Thysanura (ectognathous), 

 and in all pterygote insects. In this fact he finds — somewhat pre- 

 maturely it seems to me — a support to the symphylan theory of insect 

 descent. 



Now we should want to know how the third order of entognathous 

 apterygotes, the Protura, fits into this scheme. But the Protura have 

 no antennae ; they are the only really antennaless mandibulates, the 

 first tarsi having taken over the function of the antennae. According 

 to most authors the antennae have disappeared without leaving any 

 traces. There are, it is true, some peculiar organs on the head of 

 Protura at exactly the place where the antennae should be expected, 

 the pseudoculi, but they are most often regarded as equivalents of the 

 postantennal organs of collemboles, the Tomosvary organs of myria- 

 pods, and the pseudoculi of pauropods, which are all the same thing. 

 Paclt (1956b, p. 39) even finds that they have the same function as 

 these organs, namely, as hygrometers. He writes that "bei Anschwel- 

 lung der Hypodermiszellen des Pseudoculus wird die Form des Or- 

 gans nach aussen gewolbt." As he does not tell us whether the pro- 

 turan was living when he made his statement, nor in fact does he give 

 any other evidence, I suppose it to be a phenomenon of preparation 

 and thus not convincing. 



Handlirsch in 1926 supposed the pseudoculi of Protura to be an- 

 tennal rudiments, and in 1931 I supported this view on the basis of 

 Berlese's figures. I should want to emphasize it again on the basis 

 of a preparation of the head capsule of Acerentomon doderoi seen 

 from within. Figure i shows the pseudoculus from the ventral side 

 and more laterally from the inside of a loosened roof of the head. 

 The nerve to the organ and two muscles are seen, one originating 

 from the dorsal side of the head, the other one from below the 

 pharynx, perhaps from a mesodermal supporting structure, an endo- 

 sternum (see further on in this paper). I suppose these muscles to 

 be the antennal muscles of the organ, perhaps even able to move it, 

 which, however, I have not had the opportunity of checking on live 

 specimens. As no muscles, however, are found in connection with 

 the postantennal organs of collemboles, I find in them a proof of the 

 antennal character of the pseudoculi of Protura. And even a priori 

 I should think it much more probable that an organ such as the 

 antenna, present in every other mandibulate arthropod, should mani- 

 fest itself as merely a rudiment, rather than the postantennal organ, 

 lacking even in many groups of collemboles. 



