602 P. HERBERT OARPfciNTBR. 



(blood-vascular, auct) is frequently described by him as con- 

 tinued upwards through the ovoid gland by means of its 

 excretory canal to the level of the madreporite. He says, for 

 example, that it is " en communication avec la glande ovoide 

 et lui permet de re9evoir le sang en assez grande quantity." 

 Further on he speaks of " I'lnterposition sur un certain point 

 du trajet des vaisseaux d'un organe glandulaire, destine sans 

 doute a debarrasser le sang de produits inutiles et a les laisser 

 s'echapper au dehors a travers la plaque madreporique."^ 

 There can, therefore, be no question about the intimate rela- 

 tion of this organ with the blood-vascular system of the 

 Urchins, just as in other Echinoderms, as described by Ludwig, 

 Teuscher, myself, and others. 



This relation, however, has been denied by Perrier and 

 Apostolides, who suppose the ovoid gland not only to open by 

 its excretory duct into the sinus beneath the madreporite, as 

 described by Koehler, but also to be entirely independent of 

 any vessels whate.ver. Their observations on Asterids and 

 Ophiurids are in direct conflict with those of Ludwig ; but 

 Koehler's discoveries in the Urchins furnish a strong argument 

 in favour of liudwig's views. 



The minute structure of the ovoid gland in Urchins aud 

 Spatangids is briefly described by Koehler in the following 

 terms : — " A reticulum of connective tissue, supporting cellular 

 elements that undergo a peculiar degeneration, the final result 

 of which is the formation of numerous pigment masses." This 

 network of connective-tissue fibres is most regular near the 

 periphery of the gland, the fibres being more numerous and also 

 better defined towards the centre. It encloses alveolar spaces, 

 within which are groups of from one to four naked masses of 

 protoplasm, of an irregular stellate form. Each contains a 

 nucleus, which is of variable size. It occurs in all stages, from 

 a finely granular condition to one in which it is little else than 

 a mass of brown pigment-granules, surrounded by a thin pro- 

 toplasmic envelope, and in the peripheral region the alveoli 

 sometimes contain notbing but these pigment groups. 

 1 Op. cit., pp. Tl, 102 



