108 ü. TAKAKUKA. 



they terminate freely in the parenchymatous tissue (fig. 2). Bürger 

 noticed the undoubted existence' of the proboscis nerves between both 

 longitudinal muscle layers, but he did not enter into further detail. As 

 far as my investigation goes, it is most probable that the " Bindegewebe 

 mit zelligen Elementen," which is alluded to by v. Kennel represents 

 the nervous layer of the proboscis. It has no definite form as in other 

 Metanemertini, and is sometimes swollen and sometimes constricted, 

 and often gives off several processes between bundles of muscle fibres. 

 Numerous oval nuclei are imbedded within, or in the peripheral part of, 

 the granular looking substance, which would be the fibrous part of the 

 nervous layer. Such granular portion presents similar appearances as 

 the fibrous part of the nervous system and has the same affinity for 

 hematoxylin or eosin. 



The circulatory system shows very complex anastomoses, and 

 approaches the condition described by Blanchard 1 ' and Hoef.\iann, 2) yet 

 differs from them in some points. In young specimens it consists of 

 only three vessels, one dorsal and two lateral, as in other Metanemertini, 

 and has already been noticed by several authors (fig. 1) The two 

 lateral vessels are connected in the head by a transverse canal and 

 joined in the anal portion to two branches of the dorsal vessel (fig. 1). 

 The dorsal vessel arises anteriorly a little behind the ventral commissure 

 of the brain, by the fusion of two branches from the lateral vessels. At 

 this stage there is not yet any branch to be found. But in the adult, 

 the circulatory system reaches a degree of complication never found in 

 other nemerteans, by giving off numerous branches, which come to 

 anastomose with one another, especially in the anterior region. Figs. 3, 4, 

 and ;j, which have been reconstructed from sectious, show respectively the 

 circulatory system in the oesophageal, the middle, and the anal region. 

 The vessels invariably show a complex system of anastomoses and are 

 very asymmetrical, although there seems to be a great deal of individual 

 variation. The dorsal vessel (fig. 3, d. v.) does not appear to be 



1 ) & t). I have not had access to the works of Blanchard and Hoffmann, but I 

 gather the above from the references made by v. Kennel. 



