ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 779 



Folds of the mantle contain the organs of reproduction, and the 

 margin is provided with muscular fibres ; the mantle serves also as 

 an organ of respiration. The lacunae in the mantle which com- 

 municate with the general cavity are very simple in Crania, are more 

 complicated in Discina, and form a true gill in Lingula. The arms 

 given off from the body are free, and traversed by two canals, one of 

 which sends off branches to the cirri ; in the oesophageal region the 

 t^vo canals become very complicated and surround the digestive tube 

 with a number of lacunae ; they here communicate with one another, 

 and, by two small orifices, with the body-cavity. In addition to the 

 two protractor and retractor muscles of the arms, an important 

 bundle penetrates into their interior and ramifies in the cirri. The 

 arms are formed of a thick resisting cartilage. 



There are eleven muscles, the most important of which are the 

 two pairs which occupy the four angles of the visceral mass, and serve 

 as adductors and protractors of the shell. Four others fix the arms. 

 The anus is in the axis of the body and slightly dorsal ; the digestive 

 tube has an extremely simple structure ; the epithelium consists of a 

 single row of long ciliated cells ; the liver is also simply cellular, and 

 is invested in a sheath of delicate cartilaginous tissue in Crania; but 

 this is rudimentary in the two other genera. 



There are no proper circulatory or respiratory organs, their func- 

 tions being fulfilled by the perivisceral fluid and by other organs, 

 especially the mantle. The sexes are separate, but there are no 

 copulatory organs ; the ovaries are thickenings of the epithelium of 

 the general cavity, sustained by a kind of connective plexus. 



The nervous system of Crania and Discina consists of a delicato 

 circum-oesophageal collar ; from the dorsal part, which is slightly 

 swollen, and may be called cerebroid, the nerves to the arms are given 

 off; they contain a very rich plexus formed of cells and nerve-fibres 

 the suboesophageal portion supplies nerves to the mantle, viscera, and 

 muscles. 



On comparing the articulate with the inarticulate Brachiopoda 

 we find that, while they are sharply distinguished, there are certain 

 important characters, such as the cirri, lip, disposition of the nervous 

 system, mesenteries and gonads, which present a number of common 

 characters, variously developed in different families of either group. 



The author agrees with Gegenbaur in regarding the Brachiopoda 

 as a distinct group, but he does not seem to be aware of the opinion 

 expressed by the distinguished anatomist some eight or nine years 

 ago in his last text-book of Comparative Anatomy. In certain points 

 of organization they exhibit resemblances to Acephala, Annelids, and 

 especially Bryozoa ; these are enumerated and discussed by the author. 



Anatomy of Discina.* — M. L. Joubin has some notes on the 

 auatomy of this rare Brachiopod. The mantle is delicate, and tra- 

 versed radially by branched canals, which open by a large number of 

 small orifices into a vast intra-pallial lacuna. The peduncle is a sort 

 of oval sac, attached by its upper face to the mantle, and having the 



* Comptes Rendus, ci. (1885) pp. 1170-1, 



