REPRODUCTIVE ELEMENTS IN MYXINE GLUTJNOSA. 55 



of the characteristic polar threads; those obtained by Professor 

 Esmarck having been taken from the ovary of the female, and 

 those he himself obtained from Finmark having been given to 

 him by Mr. Buck, of Oxfjord, and also probably coming from 

 immature females. On applying to Mr. Buck himself I was 

 informed by him that he had only obtained the eggs from the 

 ovary of the female. 



The only specimens of the ripe egg in the hands of natural- 

 ists are those obtained by Professor Steenstrup, as above 

 described_, which are now in the Copenhagen Museum, and a 

 single specimen, which is in the Anatomical Museum of Edin- 

 burgh University. By the kindness of Professor Sir William 

 Turner I have had the privilege of examining the latter, but 

 as it is a unique specimen I was not able to cut it so as 

 to examine its structure. The specimen is represented in 

 Plate VI, fig 1, of the natural size. Externally it agrees 

 with the figures of Thomson and Steenstrup, except that it has 

 no indication of any separation of a part of the capsule to form 

 such an operculum as shown in the figure given by the latter 

 author. The length of the ovum is 25 mm., of the threads 

 about 5 mm. The capsule or membrane enclosing the ovum is 

 thicker at the poles than elsewhere, and the thickened portion 

 can be seen to be transparent, as shown in the figure. At each 

 pole of the ovum there is a slight conical projection, to which 

 the polar threads are attached. One of these projections, the 

 upper in the figure, is larger than the other, and it is beneath 

 this larger projection that the protoplasmic disc is situated — a 

 fact which I infer from my study of the unripe eggs. I was 

 allowed to cut off a couple of threads for microscopic examina. 

 tion. One of these is represented in fig, 1, a. The thread is 

 solid, and not tubular ; its structure, as seen under a low power, 

 appears homogeneous, and in my investigation of the develop- 

 ment of the threads I have found no indication that they are 

 tubular in any stage of growth. The statement of Allen Thom- 

 son on this point is therefore erroneous, and doubtless due to 

 his preconceived opinion that the threads were homologous with 

 the processes of the egg capsule in Elasmobranchs. 



