109 



locomotor; they are used as fins in swimming: but they are also 'out- 

 riggers', if we may so speak, serving to maintain the proper position 

 of the long abdomen while crawling about over submerged logs. " 



I examined living specimens of my Hydroptilid pre-pupae under 

 the microscope, and looked especially for evidences of gill structure 

 in the lateral appendages. I saw but few tracheae, and none of the 

 recurrent end loops of tracheoles that are characteristic of true tra- 

 cheal gills. Recently, Lauterborn and Rimsky-Korsakow have 

 studied active larvae (perhaps mine were too far gone in metamor- 

 phosis to show the same things), and have found the tracheae more 

 abundant; but one may not be assured from the rather crude figures 

 they have given whether the tracheoles anastomose at the ends to form 

 loops or not (Zool. Anz. Bd. XXVI, Nr. 694, for Feb. 23d, 1903). Be- 

 fore calling these appendages tracheal gills, I should want better 

 evidence of their oxygen gathering function than has yet been offered. 

 In the second place, Dr. Speiser implies that I found, these 

 appendages too unique »diese Tracheenkiemen, die vermutlich noch 

 manchen andern, wenn nicht den meisten Hydroptilidenlarven zu- 

 kommen«. Now, what are the known facts? There are a few cases 

 described by Fritz Müller as belonging to Hydroptilidae , from 

 Brazil, and there are a few imagos known outside the Europaean 

 fauna, such as the three so inadequately described from North America 

 by Dr. Hag en. In Europe, on the contrary, seven of the eight genera 

 are fairly well known in their difierent stages. Herr Ulmer has given 

 a key for their separation, based on the characters of their cases, in 

 Stett. ent. Zeit for 1903, p. 223. And Herr Ulmer says, in a paper 

 that Dr. Speiser cites, Stett. ent. Zeit, for 1903, p. 364, concerning 

 these appendages: »Analoge Bildungen an andern Trichopteren- 

 larven sind mir bisher noch nicht bekannt geworden (f. 



In the third place, Dr. Speiser objects to my hypothesis of 

 hypermetamorphosis, as anyone might, having the advantage of the 

 additional knowledge contributed in the papers he cites. But he 

 makes the hypothesis that my pre-pupa, which I described as lying 

 inactive in its case with head and legs folded to the left side, and with 

 its larval cuticle loosened — the latter point illustrated in figures 3 

 and 4 — was really the larva, and the other (fig. 1), which I stated 

 having seen actively walking about, was the pre-pupa; for this would 

 fit the biogenetic law and better ally this form with the Sialidae! 



The papers by Ulm er and Lauterborn and Rimsky-Korsa- 

 kow contain real contributions to science. They show, among other 

 things — what I did not know — that the young larva of Ithytricliia 

 possesses appendages like those I found upon a pre-pupa. All the 



