88 ALICE L. EMBLETON ON THE STRUCTUKE AND 



in wliicli they live ; it therefore seems likely that they are admitted to the rectum in a 

 stream of water, having a respiratory significance, and taken in through the anal 

 sphincter. The most satisfactory preparations of this tissue were those treated in 

 bulk with alnm-carmine, having first cleared the tissue of corrosive-sublimate crystals 

 by immersing it for an hour in iodine solution. I found a sort of precipitate was 

 thrown down in preparations treated in bulk with Ehrlich's ha^matoxylin, followed 

 by a stain for a few minutes on the slide of a slightly acid solution of Griibler's 

 Orange G in 70 per cent, alcohol; but otherwise these formed very excellent contrast 

 stains. 



Spengel says of Echiiirns Pallasii that the vesicles open exactly on the line of demarc- 

 ation between what he calls the "driisenlosen" and the " driisenreichen " areas; so that 

 regarding the " glandular " tissue as ejiidermal, the vesicles in this case open neither 

 internally nor externally, but on the boundary. According also to Eietsch : " L'orifice des 

 glandes anales serait exactement a la liiuite enti'e les teguments et I'intestin." The study 

 of the development of the Gephyrea, according to Korschelt and Heider*, proves that these 

 organs "do not arise, as was supposed, from the intestine, but are formed in the somatic 

 layer of the mesoderm" ; and further that " their entire mode of origin proclaims the anal 

 vesicles to be nephridia which only secondarily entered into connection with the hind 

 gut." If this is so, their function must be excretory ; and the observations of many 

 zoologists lend support to this theory. For instance, Shipley says : " The function of 

 these structures may be excretory ; or they may control the amount of liquid." 

 Danielssen and Korenf, speaking of the anal vesicles of Uaminf/ia arctica, assign to them 

 the function of nephridia, denying the possibility of their having a resj)iratory 

 significance, for they do not think the sea-water penetrates into the vesicles. 



Rietsch observes : " Quant aux fonctions de ces organs, je crois, avec H. de Lacaze, 

 qu'elles sont avant tout glandiilaires, excretoires. Les courants determines j)ar les cils 

 desentonnoirs, de la glande elle-meme et de la portion terminale de I'intestin, ue peuvent 

 donner naissance qu'a un courant vers rexterieiu\ Les glandes, en se distendant, ne 

 determinent elles pas, malgre co courant, la penetration, a I'interieur de la glande, de 

 I'eau de mer qui servirait ainsi ;i la respiration du liquide de la cavite generale ? 'A 

 priori,' la chose n'est peut-etre jjas impossible, mais I'observation directe pourrait seule 

 prouver qu'elle a rcellement lien. II ne senible pas, en tout cas, que cette eau puisse 

 par les entonnoirs aller se meter au liqviide perivisceral, surtout chez YEcliiure et la 

 Thalusseme. En somme les fonctions respiratories des glandes anales demeurent 

 douteuses." 



Huxley, Gegenbaur, Glaus, and Hatschek consider the anal vesicles as homologues of 

 the segmental organs of worms. 



Other investigators, however, have looked upon them as being undeniably respiratory 

 in function. Greeff, in his account of these organs in the Ecliiurids, begins by saying : 

 " Als llespiration-organe mtissen in erster Linie die beiden Analsehiauche betrachtet 



* Text-book of Embryolos;}- — Invertebrates, vol. i. p. 309. 



t " Fra deu norcke Nordhavs Expedition (Gephyreer)," Nyt Mag. f. Nat. Vid. vol. xxvi. pp. 44-G6. 



