332 PROFESSOR FRANK J. COL?] 



material specially fixed by intra-intani injection, in which I do not find any specially 

 modified cells associated with the possible existence of inter- or intra-cellular spaces. 

 Further, the gland cells of the pancreas have certainly not the appearance of an enzyme- 

 secreting gland, but if anything that of a mucin gland. 



The fundamental point of difference between Ma as' results and my own is that he 

 describes the secretion of the gland, whatever it may be, as discharged freely into the 

 bile duct, whilst in my material the gland is to all intents and purposes a ductless one. 

 I have no doubt we have both correctly described the material at our disposal as we 

 found it, and that the difference in our results is only one more indication of the exist- 

 ence of distinct races or varieties of Myxine glutinosa. \i is clear that the pancreatic 

 lobules represent outgrowths of the bile duct, and are hence, at least originally, in free 

 communication with it. It seems therefore that the absence of the efferent channels in 

 my material indicates a retrogressive change, and that the gland is either losing the 

 importance it formerly possessed, or undergoing some functional modification. 



Owing to the small size of the gland, and the great difficulty of satisfactorily isolating 

 its secretion, I do not think it possible to test the latter by biochemical methods. It would 

 mean dissecting it out in at least 100 specimens ; and even if this could be done in the 

 necessary time, one could never be certain that the extract was free from the secretion 

 of the liver. 



H. The Thyroid Gland (Figs. 3 and 12). 



In a preliminary paper (13) I briefly described the structure of the thyroid of 

 Myxine, under the impression that it had up to that time escaped notice. Schaffer, 

 however, pointed out that the Myxinoid thyroid had been described by W. Muller in 

 an obscure paper in 1871, and at the same time he added an account of this structure 

 in Myxine. I shall, therefore, now confine myself to such details as are omitted in 

 Schaffer's description. 



As shown in fig. 1 2, which represents a transverse section through the region of the 

 gills, there is a column of loose fatty tissue in the middle line, wedged in between the 

 gills, and extending from the gut above to the cardiac aorta below. In this column of 

 fatty tissue are embedded the small vesicles which represent an unpaired, diffuse, 

 scattered thyroid, and which can be seen with the naked eye {thy.). 



The thyroid at first sight does not appear to be an important organ in the adult. 

 In fig. 12, which in this particular series showed the maximum number of thyroid 

 vesicles appearing in any one section, only eight are seen, and the gland certainly does 

 not strike one from the point of view of size. Fortunately, however, I plotted it out 

 from my large series of sections, and the result is given in fig. 3. Nothing could be 

 more striking. The gland extends over a considerable area, both vertically and 

 longitudinally, and it includes in this individual 251 vesicles of all sizes and shapes. 

 If these were massed together into one compact gland, we should have, compared with 

 the size of the animal, a large and obviously important structure. 



