400 SUMMARY OF CURRENT RESEARCHES RELATING TO 



blood to a vast system of lacunas which is contained in tho interior of 

 the lamella?. These lacuna? arc partly occupied by connective cells and 

 fibres, and by muscular fibres, and they communicate with superficial 

 lacuna) in tho wall of the body. 



The glandular epithelium lies on a delicate basal membrane, the cells 

 of which arc arranged in a single layer ; some of these cells arc large, 

 are quite devoid of cilia, and are glandular in function, while others arc 

 ciliated and gradually diminish to a delicate peduncle which is inserted 

 in the basal membrane. The mechanism of secretion is very remarkable ; 

 the author has never seen the cells detach themselves and fall into the 

 cavity in the way which has always been described, but the excreted 

 materials collect near tho apex of the glandular cell in a vacuole which 

 gradually increases in size, and contains solid concretions. This vacuole 

 has sometimes been regarded as a second cell formed endogenously* 

 When the vacuole is sufficiently large the cell projects into the cavity, 

 and allows the vacuole to fall out. 



The glandular tissue of the kidney does not reach the pericardium ; 

 all along tho latter there is a special organ. It is a large lacuna in the 

 form of a canal, which freely communicates with the auricle ; it is 

 composed of a tissue formed of stellate connective cells, which make 

 a wide-meshed plexus. Wide ramified canals, lined by ciliated cells, 

 pass into the lacuna, and open by numerous orifices into the renal 

 cavity. 



The Orthoneura. — The memoir of Dr. H. von Ihering * on the 

 Orthoneura is critically noticed in Prof. Lacaze-Duthiers' ' Journal.' f 

 The author attempts to support the division of the Prosobranchiata into 

 Orthoneura and Chiastoneura against the criticisms of B. Haller, Spengel, 

 Biitschli, and others by an account of the arrangements which obtain in 

 the nervous system of Ampullaria. He comes to the conclusion that 

 Spengel and Haller have regarded as a visceral commissure an anasto- 

 mosis of the visceral nervous system, and he contends, therefore, that 

 the Mollusca which they studied are really orthoneurous and not 

 chiastoneurous. The anonymous critic points out that M. Bouvier has 

 shown that in Ampullaria the right commissural ganglion connected with 

 the corresponding pedal ganglion is not simple, but is equivalent to the 

 right commissural ganglion and the subintestinal ; that there is a 

 twisted visceral commissure formed by its visceral commissure, a part of 

 its visceral loop (the plexus), and by a dorsal nerve which had escaped 

 Dr. Ihering's attention ; if this be so, Ihering's argument fails, inasmuch 

 as the type which he selects is chiastoneurous itself. Bouvier has also 

 shown that the nerve which Ihering describes as arising from the right 

 commissural ganglion and going to innervate the gill is not a branchial 

 nerve, but a pallial one, and that the right gill of Ihering is always a 

 left gill, innervated by the supra-intestinal ganglion and the part of the 

 visceral commissure which unites the supra-intestinal ganglion to the 

 abdominal ganglion. 



The critic thinks that the new work of Dr. Ihering fails to establish 

 the existence of orthoneurous Prosobranchs, all of which are chiasto- 

 neurous except the Neritinaa and Helicinre, which present an apparent 

 oithoneury. 



* Zeitschr. f. Wiss. Zool., xliv. (1887) pp. 499-531 (1 pi.), 

 t Arch. Zool. Exper. et Gen., v. (1S87) pp. xvii.-xx. 



