40 SUMMARY OF CURRENT RESEARCHES RELATING TO 



is directed to the variations in colour of the liver of individuals of 

 the same species of the Placophora ; a lighter colour would appear 

 to be associated with an absence of secretory activity, and observa- 

 tions were made which led to the conclusion that the bro'mi pigment, 

 which is at first regularly diifused through the protoplasm, disap- 

 pears during the process of secretion ; the drops of secretion are 

 glass-green in colour. 



After describing the other parts of the enteric tract, the author 

 passes to the renal organ, which has lately attracted the attention of 

 V. Iliering, who looks upon it as an unpaired structure; and of 

 Sedgwick, who maintains its paired nature. Haller completely denies 

 the presence of openings from the kidney into the pericardium, and 

 supposes that the ciliated infundibular orifice becomes closed in the 

 later stages of larval life — a view which receives support from an 

 oral comuumication by Hatschek as to the course of development in 

 SijMncidus. The kidney, but not its separate lobes, are invested by 

 the peritoneum. 



The heart lies under the 7th and 8th scales, and consists of a long 

 median ventricle, which is prolonged anteriorly into the aorta, and of 

 two auricles, which pass into one another posteriorly ; it is here that 

 they communicate with the ventricle. The cardiac musculature forms 

 a plexus of many-branched anastomosing muscular bundles ; in the 

 auricles it is particularly thin, and the bundles may be there seen to 

 consist of extremely delicate fibrils ; the fibres are set parallel, except 

 at the points where the bundles branch. There is no appearance of 

 striation or of any investing layer. At the opening into the ventricle 

 the muscles form a distinct valve. The musculature is not covered 

 by any endothelium, but the muscles and the nervous elements are 

 directly bathed by the blood. As the auricles are not set freely in 

 the body, they are by that fact to be distinguished from the similar 

 organs of other Gasteropods. 



As to the course of the circulation, it is found that the blood is 

 collected from the whole primary coelom by a bilaterally disposed 

 transverse lacuna, set a little behind that of the branchial vein ; it 

 passes into a longitudinal duct, which lies beneath the nerve-cord, 

 and is set parallel to the long duct of the branchial vein. A rich 

 lacunar system, in free communication with the primary coelom, is to 

 be found in the foot. When the blood is driven out of the ventricle 

 it makes its way into the aorta, whence by simple openings (?) it passes 

 into the primary coelom, or, by pedal vessels, into the foot. The 

 venous blood from the latter is driven, by its contractions, into the 

 branchial artery, and so to the auricles. The blood-corpuscles are 

 uncoloured. 



The term secondary coelom is applied to the cavity beneath the 

 genital gland and the pericardium in which the liver and intestine 

 appear to lie ; owing to the reduction of the superior and inferior 

 mesenteries, these organs have a closed investment. These partitions 

 arc, however, present on the rectum, and prove that there are two 

 ccelomic sacs into which the digestive apparatus is invaginated. 



The author concludes with some observations on the relation of 



