576 



SCIENCE. 



[N. S. Vol.. XV. No. 380. 



of demonstrable lacuna, all lead to the 

 conclusion that the arterial and venous 

 vessels of the squid are connected by capil- 

 laries which form a closed vascular sys- 

 tem. 



The Branchial Nerves of Amhlystoma: G-. 



E. COGHILL. 



1. There is, in larval Ainblystoma, a 

 complete series of pre-trematic rami of the 

 ninth and tenth nerves. These rami are 

 distributed wholly to the epithelium of the 

 branchial arches and are therefore com- 

 parable to the pre-trematic nerves of fishes. 

 Driiner finds the same series of nerves in 

 Triton and Salamandra, and the first two 

 of the series in Proteus and Menobranchiis. 



As in some fishes, there is an anastomosis 

 in Amhlystoma between the ramus post- 

 trematicus IX. and the first ramus pre- 

 trematicus X. In some individuals there 

 is a similar anastomosis in the second and 

 third branchial arches and in the hyoid 

 arch between the facial and glossopharyn- 

 geus. The latter has been found by 

 Driiner in Triton. 



2. The I'amus alveolaris VII. of Amhly- 

 stoma is a pre-spiracular nerve and, as 

 such, cannot be homologous to the ramus 

 mandibularis internus of Anura. These 

 two nerves innervate homologous areas and 

 terminate in homologous centers in the 

 brain. They differ, however, in the follow- 

 ing important features: (a) The ramus 

 alveolaris passes antex'iorly of the deriva- 

 tiye of the spiraeular cleft, while the 

 mandibularis internus passes caudally of 

 that structure; (&) the alveolaris passes 

 dor sally of the mylohyoid muscle, while 

 the mandibularis internus passes ven- 

 trally of that muscle; (c) the alveolaris 

 anastomoses Avith the trigeminus while the 

 mandibularis does not. 



These differences may be explained by 

 reference to Squalus acanthius, in which 

 both nerves are present. Hei-e the areas 



innervated by the two nerves in part coin- 

 cide and the terminal fibers of the two 

 anastomose. Obliteration of a pre-spiracu- 

 lar nerve of the selachian type in Anura, 

 and of a like post-spiracular nerve in 

 Amhlystoma, would give the two divergent 

 amphibian types of distribution of the 

 facialis. 



The Anatomy of the Drumming Organ in V 

 some Marine Fishes: A. K. Krause. 



The Cell-Lineage of the Mesohlast-Bands 

 and Mesenchyme in Thalassema : John 

 Cutler Torrey. (Read by title only.) 

 As in many other annelids and moUusks 

 the middle germ-layer has, in Thalassema, 

 a double origin. The mesoblast-bands 

 (entomesoblast or eoelomesoblast) arise in 

 the tjrpical manner from D.4, the posterior 

 member of the fourth quartet, which also 

 contributes two small, but not rudimen- 

 tary, cells to the posterior part of the gut. 

 The "larval mesenchyme' (ectomesoblast 

 or pa}domesoblast) arises, as in most other 

 forms, from cells of the earlier or ecto- 

 blastic quartets; but whereas in the forms 

 hitherto described it arises from only one 

 quartet and only in certain quadrants, in 

 Thalassema it arises from all of the three 

 quartets and in all of the quadrants 

 (though this latter statement does not 

 apply to all of the quartets). At least 

 twenty primary ectomesoblast cells are 

 formed; but of these only ten are func- 

 tional, while at least ten are rudimentary, 

 and disappear without becoming func- 

 tional. Of the functional mesenchyme- 

 eells, three are derived from the third 

 quartet and seven from the first. These 

 give rise not only to the larval muscles, but 

 also in part to those of the adult. Of the 

 rudimentary cells, six arise from the first 

 quartet and one from each quadrant of 

 the second quartet. These cells pass into 

 the interior of the entoblast cells, are 

 absorbed, and wholly disappear. They are 



