226 DR. T. DAVIDSON ON EECENT BRACHIOPODA. 



abundance of animal nutriment than can be found in those abysses in which Terehratula 

 is destined to reside. Hence, its powers of prehension are greatei', and Cuvier suspects 

 it may even enjoy a species of locomotion from the sujierior length of its peduncle. The 

 organization of its mouth and stomach indicates, however, that it is confined to food of 

 a minute description; but its convoluted intestine shows a capacity for extracting a 

 quantity of nutriment proportioned to its superior activity and the extent of its soft parts. 

 A more complex and obvious respiratory apparatus was therefore indispensable, and it is 

 not surprising that the earlier observers failed to detect a corresponding organisation in 

 genera destined to a more limited sphere of action." 



Prof. W. K. Brooks has studied vrith great care the development of Olottidia 

 Audeharti ; and my only regret is that it is not possible here to transcribe all his 

 admirable observations. He begins by remarking thai " it has been known since about 

 the year 1860 that some of the hingeless Brachiopoda pass through a free-swimming 

 larval state. Fritz Miiller has figured and briefly described this stage of development 

 of an unknown Brachiopod from the coast of Brazil, and Mr. Crady has given a brief 

 description from memory of the swimming larva oi Lingula.'" Prof. Brooks states that he 

 obtained the larva o^ Lingula pyramidata [^=Glottidia Audeharti] in the vicinity of Fort 

 Wool during the summer, in considerable abundance, that he had succeeded in tracing its 

 development from a very early stage to the time when most of the adult characters 

 appeared, and that his observations not only show that Mr. Crady's fragmentary 

 account is correct in every particular, but also give us a very thorough acquaintance 

 with the embryo. "The free-swimming embryos of Lingula pijramidata were met 

 with in abundance at Port Wool, from about the middle of July to the middle of 

 August ; and as the youngest stages were met wdth in the early part of this period, while 

 only the older larvte were found at the end, it is probable that the breeding-season is 

 short. No adults were found until the end of July, and the reproductive oi'gans did not 

 then present any indications of functional activity, and although a number of individuals 

 were kej)t in an aquarium for several weeks, no eggs were laid, and I was unable to 

 obtain the early stages of development. The larva is enclosed between two orbicular 

 flattened valves, which are not articulated to each other, but are free round the entire 

 circumference. The dark-coloured, somewhat opaque, flask-shaped digestive organs 

 occupy the centre of the cavity of the shell, and are in contact above and below 

 with the integument which lines the valves. Around the digestive organs is 

 a body-cavity bounded externally hy the integument, which is continuous with the 

 mouth above and below, and is bent downward at right angles to the valves to form the 

 body- walls. On the sides of, and behind, and in front of the body, there is a capacious 

 mantle-chamber which is open around the entire circumference. The mouth opens in 

 the centre of a broad, flat, nearly circular disc or lophophore, around the margin of which 

 are the ciliated tentacles. The plane of the lophophore is not at right angles to the 

 long axis of the body, but inclined so as to be nearly parallel to it. The tips of 

 the tentacles may be extended beyond the edges of the valves, and thus form a 

 swimming-apparatus, somewhat like the velum of a mollusk, by the aid of which the 

 larva floats in the water or rises slowly to the surface." (See PI. XXX. figs. 7-11.) 



