ON PTYOHODERA FLAVA. 171 



tical pores as they are iu most other species of Eiiteropneusta^ 

 and indeed in most other species of the genus Ptychodera 

 itself. 



In the possession of this remarkable free pharynx P. flava 

 exhibits its close affinity with P. erythrsea, Sp., from the ^^.-^>^ 

 Eed Sea^ and P. bahamensis, Sp., as described by Spengel, 

 especially, as it would appear, with the latter. 



As in all species of Ptychodera, so here, the anterior portion 

 of the alimentary is subdivided by a deep longitudinal con- 

 striction into a dorsal, branchial, and a ventral oesophageal 

 portion. 



From what has been said above it is obvious that P. flava 

 is a very favorable species for studying the structure of the 

 pharynx, since the latter can be easily removed and examined 

 under the microscope. 



As might be supposed, there is not much anatomical detail 

 to be added to the exhaustive account given by Spengel of 

 the Enteropneustan pharynx ; but there is a point of import- 

 ance in any comparison between the latter and the pharynx of 

 Amphioxus, which is not emphasised in Spengel's monograph ; 

 in fact, so far as I can ascertain, he makes no reference to it 

 whatever, and yet it is of prime significance. 



On examining the pharynx of P. flava one cannot fail to 

 be astonished at the relatively enormous size of the tongue- 

 bars as compared with the primary or septal bars (fig. 3). 

 The former are wide, opaque, dark brownish coloured struc- 

 tures, while the former are narrow and semi-transparent. 

 The contrast between the primary and tongue bars in point of 

 size and appearance could hardly be much greater than it is in 

 P. flava. 



In fact, it may be stated categorically that in the Entero- 

 pneusta in general (as shown by SpengePs figures), and in P. 

 flava iu particular, the tongue-bars are much larger than the 

 septal bars ; while in Amphioxus, as is well known, the reverse 

 condition obtains, in that the primary bars are larger (but not 

 so much larger) than the tongue-bars. 



This is a most important difference, not only in an ana- 



