ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 791 



author differs from most embryologists. He supports (against 

 Ludwig) the view, formerly urged by Lyman, that the oral skeleton 

 is not made up of modified proximal elements of the arms, since it has 

 an earlier and independent origin. The alimentary canal he describes 

 as formed by delamination, not by invagination as in other echino- 

 derms. Lastly, he contends that the two (rarely three) rudiments, 

 from one of which the future water-system is derived, do not arise as 

 diverticula of the digestive tube, but from cells which lie between it 

 and the ectoderm of the embryo. 



Formulae for Coniatulidae.* — Professor F. Jeffrey Bell in an 

 " Attempt to apply a method of formulation to the species of the 

 Comatulid^e," deals with the two large genera Antedon aud Actino- 

 metra ; these two forms he proposes to distinguish by the signs A and 

 A' ; while for the brachials, distichals, and palmars he uses the letters 

 B, D, and P, whenever their respective axillary forms a " syzygy " ; 

 according as the first, second, or third brachial is a syzygy he adds 

 the number 1, 2, or 3. Dealing with the cirri and their joints he 

 divides both into three sets of few, moderate, or many ; these are dis- 

 tinguished by the letters a, b, and c, the cirrus-mark being placed 

 above and the joint-mark below the fraction sign. A ten-rayed 

 Antedon with 15 cirri of 40-50 joints, with the first syzygy on the 



third brachial, has its formula written 3 A - ; a multiradiate Adino- 



c 



metra with its radial and palmar (though not its distichal) axillaries 



syzygies, with a syzygy on its first brachial, with less than 13 cirri 



and more than 40 cirrus-joints, has the formula 1 A' K P -. When a 



character is not constant it is placed in brackets, and when a multi- 

 radiate species has not any axillary in E, D, and P, its formula is 

 placed under the mathematical sign of the square root. 



Holothuroidea of the Norwegian North Sea Expedition. f — In 

 another magnificent contribution to the fauna of the Arctic Seas, 

 D. C. Danielssen and J. Koren describe in detail the new forms of 

 which they have already published diagnoses. Of the seventeen 

 genera in the collection five were new, and of the twenty-five species, 

 six were new. Kolga hyalina is remarkable for the absence of fibrillar 

 tissue from the subepithelial connective tissue, an arrangement known 

 in no other Holothurian ; the calcareous ring is very imperfectly 

 developed, and the sand-canal presents au embryonic condition in still 

 remaining open ; the bilateral symmetry of this form does not, in the 

 opinion of the authors, weigh sufficiently against the totality of their 

 organization, to justify us in placing it high in the scale. In Tro~ 

 chostoma tlwmsonii well-defined vascular plexuses were seen in the 

 wall of the rectum, but they do not seem, as in some insects, to have 

 a respiratory function, but to serve as a system of lymphatic vessels. 

 Two respiratory tubes are connected with the intestine, but there is 

 no proper cloaca ; the madreporite is remarkable for its position, being 



* Proc. Zool. Soc. Lond. 1882, pp. 531-6 fl pi.). 



t Norske Nbrdhava Exp. 1S76-S, vi., Zoology, 4to, 90 pp. (13 pis. and 1 map). 



