ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 247 



round tlie aboral circle, and in each interradius give off two branches which 

 pass to the interior of the cajcal vessels belonging to two contiguous arms. 

 Within the aboral circle and its genital vessels there is therefore a central 

 cellular cord ; this swells at the end of the vessel and becomes considerably 

 developed, forming the genital organ which is completely surrounded by a 

 sinus ; the cells of the cord give rise to ova or spermatoblasts. An invagi- 

 nation of the integument now comes to meet the genital organ, which it 

 finally puts into communication with the exterior. 



This cord is directly derived from, and has the same structure as the 

 ovoid gland ; the ovum is morphologically the homologue of the blood- 

 corpuscles, and the ovarian cells which do not become ova altogether re- 

 semble blood-corpuscles ; a similar development does not take place in the 

 testis. 



The ovoid gland gives rise to yet another structure which appears 

 before the genital organs ; this is a glandular process which perforates the 

 interradial sinus near its aboral extremity, and extends freely into the gene- 

 ral cavity. Luidia ciliaris has one, Asterias ruhens and others two, and 

 A. glacialis three ; they are totally wanting in Cribrella and Echinaster ; 

 Hoffmann and Ludwig have regarded them as intestinal vascular plexuses, 

 and Jourdain as an excretory gland, but the author looks on them as 

 belonging to the same group of lymphatic glands as the bodies of Tiede- 

 mann and the Polian vesicles. 



Twelve-armed Comatula.* — Mr. A. Dendy gives a description of a 

 female specimen of Antfidon rosacea, in which one of the arms of each side 

 bifurcates, giving twelve arms ; with the mouth as anterior and anus as 

 posterior, the third right arm and the fourth left arm are the abnormal 

 ones. The second brachial of each of these resembles in shape the third 

 radial plate, and carries on each side a third brachial, which is the starting- 

 point for the new arm. Each of the two third brachials has a syzygy upon 

 it. The two extra arms are supplied with ambulacral grooves, and the 

 author suggests that it is due to these extra means of obtaining food that 

 the specimen is of such a large size. 



Morphology of Antedon rosacea.f — Dr. P. H. Carpenter calls attention 

 to that portion of MM. Vogt and Yung's ' Traite d' Anatomic pratique ' 

 which deals with Antedon rosacea ; he points out a number of errors of 

 omission and commission which might have been saved by an acquaintance 

 with what has already been published on the subject by writers other than 

 Prof. Perrier. 



Supposed Symbiotic Algae in Antedon rosacea. | — Dr. P. H. Carpenter 

 criticizes the theory of Messrs. Vogt and Yung that the sacculi of Antedon 

 are zooxanthellse, and urges arguments against this view ; attention is also 

 drawn to the errors made by Perrier in the introduction to his new memoir 

 on Antedon. 



Coelenterata, 

 Function of Nettle-cells. § — Dr. E. von Lendenfeld suggests that there 

 can be but one explanation of the mode of action of, at any rate, the larger 

 kind of nettle-cells or cnidoblasts ; its structureless peduncle is a support, 

 and may contract so as, under certain circumstances, to withdraw the cnido- 

 blast from the surface ; control over their movements is probably effected by 



* Proc. E. Pliys. Soc. Edin., cxv, (1885-6) pp. 180-3 (1 pi.), 



t Ann. and Mag. Nat. Hist., xix. (1887) pp. 19-il. 



% Quart. Journ, Micr. Sci., xxvii. (1887) pp. 379-91 (1 fig.)- 



§ Ibid., pp. 393-9 (1 fig.). 



