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MISCELLANEOUS. 



On the Morphology and Affinities of the Brachiopoda. 

 By H. Lacaze-Duthiers. 



Few animals are so widely diifused in the strata of the surface of 

 the globe as the Brachiopoda, and few consequently are so frequently 

 in the hands of naturalists ; nevertheless, although they are repre- 

 sented by many species living in our seas, their zoological relations 

 and their general plan of organization are by no means agreed upon. 



Placed in the first instance among the Acephala, side by side with 

 the Lamellibranchiata, they now justly form a distinct division ; but 

 the relationships of this division are far from being the same in the 

 eyes of all zoologists. Thus, to dwell only upon the last opinion, 

 Messrs. Huxley and Hancock, two of the most eminent English 

 naturalists, would place them among the Molluscoida, by the side of 

 the Ascidia and Bryozoa or Polyzoa. 



This new mode of appreciating the affinities of this group led me 

 to desire to study these creatures afresh ; and when the opportunity 

 was afforded me of investigating the faunas of great depths in the 

 Meditterranean, I hastened to resume observations commenced about 

 1858 in the sea off Corsica. 



To determine the affinities of the Brachiopoda I seek in their 

 nervous system for the criterion that must guide me. It is to the 

 characteristic organ of animality that I apply myself, because, as has 

 been so admirably shown by Cuvier, it furnishes the characters of 

 highest value ; and I compare it on the one hand to that of the 

 Lamellibranchiata, and on the other to that of the Bryozoa. 



In the Lamellibranchiate Acephalan the plan of organization is 

 simple. The organs are repeated symmetrically on each side of the 

 median line. Thus we find three double nervous centres — one near 

 the mouth, another in the foot, the third between the base of the 

 foot and the anus, near the branchiae. Moreover certain organs 

 have an existence, a peculiar symmetry, and very precise relations 

 with these different centres. 



Upon the median line are the mouth, the foot, and the anus. At 

 the base of the foot, between it and the anus, on each side, beyond 

 the ganglia of the third or pallio-branchial group, open the two 

 glandular bodies called the glands of Bojanus ; lastly, to the right 

 and left of the mouth there are two pairs of labial vela, which vary 

 greatly in form in the different species. 



To compare this well-known plan, which it was necessary to refer 

 to here, with that of the Brachiopods, we must first of all place the 

 animals in a comparable position. Suppose, for example, that we 

 have a Terebratula and an Anodonta to compare : the former must 

 be placed with its ligament downwards, its apophysary valve to the 

 left of the observer, and its perforated valve to his right ; the second 

 must have its hinge to the left and its mouth upwards. Most 

 figures show the Brachiopoda in a position the reverse of that just 

 indicated, which renders their comparison with the Acephala more 

 difficult. 



