DR. T. DAYIDSOX ON EECEXT BRACIIIOPODA, Kil 



power, as tlio walls avo so dcliratc; whilst the calcified portion of the mantle is very 

 thick, of a dull white colour, apparently of a spongy nature, and under the same 

 enlargement seems to us much nun-e compact than even the walls of tlio shell. In oi-dcr 

 to realize the diverse condition of the mantle thus calciGcd, we must call to our aid high 

 magnit'ying-])owcr. 



]\I. Lacaze-Uuthiors states, in the work previously quoted, that the so-termed " oral 

 arms " or lal)ial appendages of Thocidium resemhle those of other Brachiopoda, except that 

 they are not free, hut adhere throughout their extent ; that the swollen basis certainly 

 presents a canal similar to that which exists in the other animals of the same group, and 

 that this longitudinal canal is present throughout their length, heing almost confounded 

 with the mantle, or with the margin of the body, and is even located in the insertion of the 

 arms. These "arms" are inserted by their basis, not on the intermediate or lateral 

 lamella, or external lamella (" descending crescent-shaped processes "), but on the edge 

 of the "ascending apparatus." Their direction is that of the lamina on which they are 

 supported ; and they reach, after having described the inflections already indicated, the 

 median point of the tongue-shaped process, where their two extremities arc located. This 

 arrangement is shown in PL XXIII. fig. lO, Avhich is copied from one I published first 

 in the 'Annals and Magazine of Nat. Hist.' for May 1852, and afterwards reproduced in 

 Dr. AVoodward's ' Manual of the Mollusca.' The cirri of the arms are long and flexible. 



Space will not permit us to follow M. Lacaze-Duthiers in bis admirable observations in 

 connection with the anatomy of the animal, further than to say that he minutely describes 

 the position of the animal in the shell, the mantle, muscles, the organs of nutrition, the 

 arms and their cirri, the moutli and its lips, the liver, stomach, intestines, circvilation, 

 respiration, the special glands, nervous system, the male and female organs of repro- 

 duction, &c. He adds, that French zoologists consider, with some other naturalists, 

 that respiration is probably effected partly by the labial appendages, which bear a 

 great analogy to the gills of other Mollusca, and that he has not been able to discover 

 any anal aperture — a fact strongly urged by Messrs. Huxley, Hancock, Gratiolet, 

 and others for Terehratula and EliynclioneUa. M. Lacaze-Duthiers is of opinion that 

 the sexes are distinct, or, in other words, that there is a male and female animal; but 

 Mr. Hancock considers this to be uncertain, and is disposed to hold the opinion that the 

 sexes are combined in the same animal. 



M. Lacaze-Duthiers concludes his elaborate series of anatomical observations with 

 many important details in connection wdth the embryonic condition of Thecklmm medi- 

 terraneuin, but states that it was not possible for him to follow out in a complete manner 

 every successive stage of its development. The youngest egg that he was able to 

 observe had already acquired a rather elongated pyriform shape, and what attracted 

 most notice was the large size of the cells of which it was composed, which also 

 contained a large quantity of granulations, of a comparatively enormous size. 

 The egg at this stage is very similar, at least in general appearance, to a mass of 

 vegetable cells full of feculse. Towards one of the extremities of the egg the connection 

 with the bourlet or cap of the suspensory filaments may be found, and however little 



