B-1LA3TOGLOSSUS. TEEMES. 303 



which give off numerous transverse branches to the walls of the 

 intestine and body, and of two lateral trunks. The branchire receive 

 their rich vascular supply entirely from the lower trunk. The upper 

 trunk, in which the blood flows from behind forwards, divides at tho 

 posterior end of the branchiae into four branches, of which the two 

 lateral ones pass to the lateral portions of the anterior part of the 

 body. 



Certain fibrous cords, running directly beneath the epidermis in the 

 dorsal and ventral median lines and branching into a net-work of fine 

 fibrillse, have lately been interpreted as nervous centres. These cords 

 are described as being connected at the posterior end of the collar by 

 a ring-like commissure. 



The generative organs are arranged in single rows in the branchial 

 region, but posterior to this in double rows. During the breeding 

 season they are extraordinarily developed, and the male and female 

 can be easily, distinguished by the difference in their colour. Each 

 ovum is contained in a capsule, which is provided with nuclei, but is 

 otherwise homogeneous. The eggs are probably laid in strings like 

 those of Nemertines. 



These animals live in fine sand. They saturate the sand in their 

 immediate vicinity with mucous. They fill their alimentary canal 

 with sand, and move themselves by means of their proboscis, which, 

 alternately elongating and retracting, draws the body after it. 

 Both the species named were found in the Gulf of Naples. A third 

 northern species of Balanoylossus was discovered by Willenioes-Suhm, 

 and described as B. Kupfferi. 



CHAPTER IX. 



YERMES. 



Bilateral animals with unsegmented or uniformly (Jiomonomsus) 

 segmented body. There are no segmented lateral appendages. A 

 dermal muscular system and paired excretory canals (water-vascular 

 system) are present. 



SINCE the time of Cuvier, a number of groups of animals all 

 characterised by the possession of an elongated laterally symmetrical 

 body and by the absence of articulated limbs have been classed 

 together as Vermes. This group includes such a variety of forms 

 that attempts have already been made to break it up, and it will 

 perhaps be necessary at some future time to separate the unseg- 



