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Tlie Pseudobrancliial Circulation in Amia calva. 



By 

 Edward Phelps Ulis jr. 



With Plate 6. 



Shortly before Friedrich Müller's work "Ueber die Entwick- 

 lung und morphologische Bedeutung der 'Pseudobrauchie' und ihre 

 Umgebung bei Lepidosteus osseus" was published, I had sent to the 

 press the manuscript of the following article in much the form in 

 which it now appears. Unfortunately this manuscript was lost in transit, 

 but I did not know of it until nearly a year later, when I wrote 

 asking why it had not yet been published. The manuscript having 

 been lost I decided, because of Müller's work, not to publish anything 

 relating so entirely to this especial subject. In going over the work 

 again, I find, however, that it forms a somewhat important chapter 

 in my work on Amia\ and that, moreover, as my observations relate 

 to a different fish, there is nearly as much reason for their public- 

 ation now as there was before the appearance of Müller's paper. 



My attention was first especially drawn to this subject, incidentally, 

 while studying the development of the skull in 12 mm embryos of 

 Amia^ where I noticed that there was no perceptible arterial con- 

 nection between the pseudobranch and the external carotid artery. As 

 this connection was found to be wanting in all my series of sections 

 of that age I concluded that it could not be due simply to some 

 effect of reagents, or to some defect in the sections, and I was ac- 

 cordingly led to examine certain older and younger stages, and finally 

 to investigate the subject as fully as the material I had at the time 

 at my disposal would permit. This material, in so far as it related 

 to the earlier stages in the development of the pseudobranchial arteries, 

 was most incomplete and imperfect, but I did not then, and have not 

 now, attempted to make additional preparations, as the results ob- 

 tained seem to me sufficiently definite without them and their pre- 



