122 ISABELLA M. DRUM MONO. 



other they come uearly iuto contact with the horns of the 

 mantle cavity, but no communication is formed. Instead, 

 each kidney communicates with a sort of little vesicle, as 

 seen in fig. 20, which at the same time shows the close 

 approximation of the horn of the mantle cavity to the 

 kidney on either side. Below the kidneys, that is, nearer to 

 the anus, these two vesicles unite, and run back for a short 

 distance as a single duct, which opens into the mantle 

 cavity mid-dorsally, as shown in fig. 21. Shortly afterwards 

 the anus opens on the same mid-dorsal ridge. 



One further feature remains to be noticed, namely, the 

 absence of liver. The stomach is well developed, but the 

 only trace to be found of anything which might be interpreted 

 as liver is a pair of little outgrowths of the alimentary canal 

 just in the region where the stomach and oesophagus unite. 

 These are shown in fig. 22. If these may be so interpreted, 

 then the liver shares also in the symmetry shown by the 

 mantle cavity and kidneys. The visceral connectives, as 

 would be expected, run back perfectly symmetrically beside 

 the oesophagus. 



3. Other monstrosities occurred, but of less interest than 

 the above. They all showed traces of symmetry in a greater 

 or less degree, and some of them the same tendency to 

 exogastric coiling, but in most cases the organs were 

 deformed, and very much less clear of interpretation. Only 

 one other, therefore, is shown here (fig. M iii). This one is 

 remarkable in that a greater degree of symmetry than is 

 usual is combined with a slight sinistral torsion, and a fairly 

 well-marked development of the mantle cavity to the left ol: 

 the original left horn, as seen in the figure. The symmetry 

 of the body is, however, confused, in that the pericardium is 

 more developed on the right side than on the left. This 

 embryo is further remarkable in that it is the only one of 

 the monstrosities possessed of a clearly defined liver, which 

 even in this case is very small, and hangs like a sac from the 

 stomach ventrally, and slightly on the right side of tlie 

 body. 



