176 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the pericardium and nephridia of Mollusca, for these are certainly deri- 

 vatives of the primitive genital ducts. Save for its secondary relation 

 to the sexual products, the coelom of Annelids is a schizoccele. 



Mollusca. 



North Atlantic Molluscs.* — H. Friele and J. A. Grieg conclude 

 their report on the Molluscs of the Norwegian North Atlantic Expedi- 

 tion (1876-1878), and this part is the last of the whole series. The 

 first volume on molluscs treated of the Buccinidse, the second of the 

 genus Bela and some new or rare forms, the concluding volume takes a 

 faunistic survey of all the species collected, with information respecting 

 their horizontal and vertical distribution. The list includes 108 Bi- 

 valves, 8 Scaphopods, 10 Placophora, 22 Nudibranchs, 5 Pteropods, 192 

 other Gastropods, and 7 Cephalopods. 



Diverticulum of Duct of Spermotheca in Helix aspersa. f — Do- 

 mingo Sanchez gives a detailed description of this well-known diver- 

 ticulum. He distinguishes three longitudinal regions and two distinct 

 strata in its wall. 



Papillee of Eolidse.| — Ernst Krembzow has investigated the struc- 

 ture and development of the dorsal appendages of Eolis exigua, and has 

 checked his results by a comparison with some other members of the 

 same family. Much of the interest of the research is concentrated in 

 the question of the origin of the " cnidophore-sac " — regarded as ecto- 

 dermic by Herdman, as endodermic by Davenport. The author's 

 results confirm those of Davenport. He finds that the liver contains 

 undifferentiated cells of embryonic type, which form the future cnido- 

 blasts, and these grow out into the ectodermic iuvagination which forms 

 the first rudiment of the papilla. Into the space between ectoderm and 

 endoderm in the developing papilla mesenchyme cells find their way. 

 As the endoderm grows out into the papilla, however, it is seen to con- 

 sist, not only of the embryonic cells mentioned above, but also of a 

 certain number of true liver-cells. Between the distal embryonic cells 

 — now rapidly undergoing differentiation into cnidoblasts — and the 

 proximal liver-cells a furrow appears, and here the mesenchyme cells 

 form the sphincter muscle. The cnidophore sac then acquires an 

 opening to the exterior, and the cnidoblasts, few in number but of large 

 size, each produce numerous stinging capsules, a process initiated at an 

 earlier stage. Certain cells which lie between ectoderm and endoderm, 

 regarded as mucus-secreting by Herdman, the author believes to have 

 arisen from liver-cells. In Eolidiella glauca the cnidoblasts differ in 

 form, number, and arrangement from those of Eolis exigua. They are 

 •more numerous, long and narrow in shape, and do not begin to form 

 capsules until a relatively later stage. In both the forms mentioned 

 nematocysts are produced in the liver as well as in the papillae. 



Free Intra-epithelial Nerve-endings in Helix. § — Dr. H. Smidt 

 begins his communication on this subject by noting that while free 



* Norske Nordhavs Exped., xxviii. (1901) xviii. and 131 pp., 2 figs., and a map. 

 + Boll. Soc. Espan. Hist. Nat, i. No. 10 (1901) pp. 380-5 (1 fig.). 

 t Arch. Mikr. Anat., lix. (1901) pp. 181-210 (2 pis.). 

 § Anat. Anzeig., xx. (1902) pp. 495-506 (8 figs.). 



