190 ox THE MORPHOLOGY OF THE CEPHALOUS MOLLUSCA 



A hollow sacculated organ, with yellowish glandular parietes, sur- 

 rounds the base of the pulmonary sac in the Pulmonata, and opens by 

 the side of the rectum. The secretion of this organ has been shown 

 to contain uric acid.^ No contractions have been observed in it. 



In FiisHs, Cyprtxa, and other Pectinibranchiata, an aperture, fre- 

 quently seated upon a kind of papilla placed at the posterior and 

 upper part of the branchial chamber, leads into a wide cavity, which is 

 in relation above with the pericardium, and on the sides with the 

 rectum and generative duct. In its anterior wall a yellow gland is 

 frequently attached, which consists of large vascular laminse. I 

 observed no contractions of either the sac or the yellow gland, but my 

 attention was not at the time particularly directed to this point. 



Xow I think that this sac, with its vascular gland, is exactly com- 

 parable in position to the " contractile sac " and to the renal .organ of 

 Pulmonata, while, on the other hand, it closely resembles the serous 

 chambers with their contained venous appendages, which open into 

 the mantle-chamber of the Cephalopoda. 



The venous appendages of the Cephalopoda, however, have been 

 demonstrated to be renal organs by containing secreted uric acid, and 

 they possess the faculty of rhythmical contraction.^ 



The chambers of the venous appendages, then, in the Cephalopoda 

 answer to a " contractile sac," in which the secreting power and the 

 contractile faculty have become restricted and localized in a portion 

 of the organ.^ 



I have here touched mainly upon the less commonly understood 

 portions of the internal anatomy of the Cephalopoda and Gasteropoda, 

 but they clearly tend to strengthen the conclusion to be derived from 

 embryology and the more generally known anatomical facts, viz., that 

 the Cephalopoda and Gasteropoda are morphologically one, are modi- 

 fications of the same archetypal molluscous form. 



On the other hand, I have made no reference to the Acephala, nor 

 is it my intention to go into that part of the subject ; but, for the sake 

 of the zoological bearings of the question, I may shortly express my 

 belief, that of the two families of the Acephala, there is abundant 

 evidence, both anatomical and embryological, to show that the one, 



^ H. Meckel, Miiller's Archiv, 1846. 

 - Kolliker, Entwickelungsgeschichte A. Cephalopoden. 



^ A renal organ of similar character has been long since demonstrated in the Lamelli- 

 branchiata. (See Von Siebold, Vergl. Anat. ) 



