Morse.] 328 [March 19, 
arrangement, the fact that in Lingula and Discina and allied forms 
the shells have their borders free all round, while in those that 
interlock at their posterior margins, there is no ligament to act upon 
them, as in the lateral shells of the bivalve Mollusk, all these features 
together preclude the possibility of any comparison between them 
and the molluscan shell. It is, therefore, more natural to regard 
the Brachiopod shell as a dense and thickened integument, to be 
compared to similar regions in the Arthropods and in the worms, 
simply as dorsal and ventral plates, and from certain considerations 
to follow, we believe this relationship will be admitted. The pres- 
ence of nearly fifty per cent. of phosphate of lime in the test of 
Lingula, both recent and fossil, is a feature peculiar to the hardened 
integuments of the higher Arthropods, and entirely unlike anything 
found in the molluscan shell. In the hardened intecument of Crusta- 
cea, tubular pores exist, which according to Dr. C. De Morgan! are 
organs of general, or special sensibility, as he finds in many cases 
the tubules surmounted by hairs. 
He says, “ The shell canals are comparatively fine, more resem- 
bling coarse dentinal tubes, but they are lined by a sheath, and have 
contents prolonged from the vascular layer. The relations of the 
contents of the tubes to the internal integuments, may be shown by 
tearing away the latter from the shell, when the contents will often 
be drawn out of the canals; and it may be seen that they are pro- 
longations of the outer layer of the integument, enclosing the ele- 
ments of the vascular layer within their cavities.” 
In the Annelida, also, there appears a system of minute pores, 
and Kolliker (we copy from Claparede) asks whether they are not 
homologous to the tubular pores (porenkandile of the Germans) of the 
Arthropods, or whether they may not be compared to the apertures 
of the cutaneous glands, such as those discovered by Mr. Leydig in 
the Piscicole. To this, M. Claparéde says, positively, that the two 
categories of pores exists in the Annelida. Those which serve for 
the discharge of certain secretions seem to exist in all species. He 
says, furthermore, that the canalicular pores are much smaller, and 
much closer together, and do not correspond with glands, and that 
they occur only in the species with a thick cuticle, and not even in all 
these. 
In the test of most Brachiopods, similar minute tubular canals 
1Qn the structure and functions of the hairs of the Crustacea. Phil. Trans., Lon- 
don, Vol. 148, Pp. 897. 
