LIVING HRACIIIOPODA. 325 



muscular attachment. That the coecal tubules are sensory organs of some sort seems 

 highly probable. Sollas ('86-'87) has figured a coecal tubule, in section, of Waidht-lmiu 

 <-ni /i i a in and shows a structure which he interprets as an organ sensitive to tactile 

 impression. In my Embryology of Terebratuliua ('73a), I compared these processes with 

 what I regarded as an analogous structure in the test of Crustacea and considered them. 

 as organs of general sensibility. In this memoir I describe and figure in a very early 

 stage of T. septentrionalis, veritable tenuous, hair-like processes, to the number of ten 

 or more, radiating from the distal terminations of the first three tubules formed. 

 Bemmelen ('83) suggests that I may have made a mistake in my observations of their 

 displacement by a delicate brush. I can assure this accomplished naturalist that there 

 was no mistake about the observation, though I agree with him that the hairs can have 1 

 no relation to the radiating tubules described by King ('70). In my earlier memoir 

 (71) I figure and describe two short ramifications from the end of one tubule, which 

 are probablv comparable with the radiating tubules of King and probably with those of 

 Carpenter ('00). In the earlv stage of Terebratuliua, not only is the shell raised in 

 a shallow collar about the external end of the tubule, but a yellowish glandular plug is 

 seen from which radiate these delicate hairs. Claparede (V>',l) figures certain papillae on 

 the elytra of Polynoe with cirri terminating in hairs, reminding one strongly of the 

 features above described. In this connection it may be interesting to state that Davidson 

 ('Sti-'SS) describes a species of Crania from the Permian of England of which he says in 

 the dorsal shell, "externally the entire surface is closely crowded by a multitude of 

 minute, short, hollow, spinulose tubercles which produce a granulated aspect." The 

 manner in which the ridges in Terebratulina coincide with the setae may explain the 

 spinous character in certain forms of Productus and other fossil brachiopods ; but in 

 Crania there are no setae, and it would be an interesting inquiry as to the origin and 

 function of these hollow, spinulose tubercles. 



PEDUNCLE. 



The peduncle is a characteristic feature of the Brachiopoda, though wanting in many 

 Testicardine forms and in Crania. That the early stages of this interesting animal will 

 show the presence of this structure, there can be no doubt. An examination <>f the shell 

 of Crania shows no traces of a peduncular foramen, and it is probable that in the young 

 stage the peduncle will be found projecting between the shells, as in the Lingulidae. It 

 will be interesting to observe the attitude of the terminal end of the intestine in relation 

 to the peduncle, for in Crania alone, among the brachiopods, the intestine terminates 

 posteriori}' and not at the side, as in Liugula and Discinisca. 



