88 University of California Publications in 



though the possibility exists that in some it may have been 

 present, and have been torn off in dissection. Polyodon has a 

 very deeply pigmented pial covering of the brain, but it remains 

 thin and membranous over the fourth ventricle. I myself ex- 

 posed several brains of Amia with the myelencephalic gland 

 especially in mind and found no trace of such a gland there. 

 This was unexpected, since Amia is without doubt the form 

 nearest allied to Lepisosteus. 



In an article on the central nervous system of Protoptcms 

 annectens, only the preliminary report of which was accessible 

 to me, Burckhardt (1892) figures the dorsum of this dipnoan 

 brain with a structure possessing numerous diverticula lying 

 over the hind-brain, which he calls the "saccus endolymphat- 

 icus." This figure is reproduced by Wiedersheim (1909, fig. 

 20lA, p. 296). In a longitudinal section of the same brain (fig. 

 202e in Wiedersheim) this "saccus" has seemingly been re- 

 moved, as the myelencephalon is covered only by the much folded 

 choroid plexus. Whether or not Burckhardt 's "saccus endolym- 

 phaticus" of Protopterus is in any way related to the myelence- 

 phalic gland in Lepisosteus, I am unable to say at the present 

 time, but judging from the name and its appearance in the 

 figure, it is highly improbable. If this should be found to be 

 homologous, it is all the more strange that it does not appear 

 in Amia. 



The general form of the gland in Lepisosteus osseus is not 

 bilobed as described by Herrick (1891), but it is trilobed. 

 The main body of the gland is slightly wider than long, and is 

 thickened just cephalad of the middle, sloping off towards the 

 front and back, and with a pronounced median sulcus caudally, 

 causing the posterior border to be emarginate. From the antero- 

 lateral angles there projects on either side an ear-like lobe, very 

 definite and constant in shape and size, connected with the main 

 body by a rather slender neck (fig. A). These ear-like projec- 

 tions are entirely surrounded by cartilage, making their dis- 

 section rather difficult, although they readily hold their shape 

 and position when freed from the cartilage. 



