IV. Ophiuroideu. 7 



Ludwig are processes of the ovoid gland which pass through the walls of the axial 

 sinus and hang into the coelom , supplying it with blood-corpuscles. They are to 

 be considered as lymphatic glands and as comparable to Tiedemanu's bodies and 

 Polian vesicles. 



The cousins Sarasin( 2 ) have found a new species of Stylifer infesting Line/da 

 multiforis. It occupies a pouch like cavity beneath the integumental calcification, 

 which causes the peritoneum to project into the coelom and communicates with 

 the exterior by a small opening, through which the apex of the shell is visible. The 

 proboscis of the S. penetrates into the surrounding tissue and obtains nourishment 

 from the coelomic fluid. This Linckia is also remarkable for its powers of regene- 

 ration, new arms being readily formed, sometimes with bifurcating ends [see 

 Herdmau in Bericht for 1880 Ech. p 9]. Sometimes, however, a small new star- 

 fish is developed at the end of the regenerating arm, as if indicative of a tendency 

 to form a colony. 



IV. Ophiuroidea. 



See also Hamann(', 3 ), supra, p 3, Kohler, supra, p 4, & Preyer, supra, p 1. 



Kdhler's account of the structure of the water- vascular system in Ophiurids 

 differs in many respects from that given by Apostolides [see Bericht for 1882 I 

 p 189]. The outer coat of the radial vessels consists of connective tissue fibres, 

 within which is an elastic membrane. Inside this are the longitudinal muscular 

 fibres, with a few circular ones, and the whole is lined by a ciliated epithelium. 

 In the Polian vesicles the outer coat of connective tissue is much thicker , and it is 

 separated from the elastic membrane by a strong muscular sheet; the tube-feet 

 have the same general structure as the radial vessels , together with an epithelial 

 covering in which sensory cells may be distinguished. The ring-like space round 

 the mouth, described as the inner perihaemal canal by Ludwig, is merely a closed 

 cavity contained in a fold of the gastric wall , and occupied by cellular elements 

 identical with those in the coelom. The ring-space, termed by Ludwig the outer 

 perihaemal canal, is divided by a septum into two parts both of which extend into 

 the arms ; the outer or dorsal one is the larger, and contains both nerve and blood- 

 vessel. It is a schizocoel, but seems to communicate with the dorsal coelom of the 

 arms, and contains the same cellular elements. The nerve tracts are separable 

 into two regions, fibrous and cellular, the latter being on the ventral side, and 

 situated immediately above the transverse septum in the perihaemal space ; a sheet 

 of connective tissue covers the dorsal face of the nerve. The dorsal organ or 

 madreporic gland has no excretory canal placing it in communication with the 

 exterior as described by Apostolides; but it terminates below in 2 slender processes 

 which are attached to the inner face of the mouth-shield . It is composed of anasto- 

 mosing fibres of connective tissue which support irregular cells containing pig- 

 ment, this being more abundant towards the periphery. The dorsal organ is 

 surrounded by an envelope which varies in development in different genera. In Ophio- 

 glypha texturata it is closely applied to the inner face, but separated from the outer 

 face by a distinct cavity, which opens into the oral perihaemal ring and represents 

 the axial perihaemal canal of Asterids. In like manner the upper end of the dorsal 

 organ joins a vascular circle situated within the oral perihaemal ring and formed by 

 a meshwork of connective tissue fibres supporting pigment cells ; the radial trunks 

 proceeding from it have the same structure. These statements confirm and ex- 

 tend those of Ludwig [see Bericht for 1880 I p 201], but K. has been unable to 

 find any trace of the aboral blood- vascular ring described by him [see Hamann, 

 infra, p 8]. The so called vascular system of the Ophiurids is not so much a 



