568 RECORD OF CURRENT RESEARCHES RELATING TO 



margin. On either side of the head there is a long tentacle, pro- 

 vided on its anterior surface with cylindrical papillse. The segments 

 of the body are numerous, and gradually decrease in size as they 

 proceed backwards ; terminally there is a broad papilla with a style- 

 shaped appendage on either side and bounding the anus. The body 

 may be divided into two distinct regions ; the anterior one is pro- 

 vided with nine double pairs of bundles of setae, and in this point 

 presents some resemblance to Heterospio longisshna, described by Ehlers. 

 The sette of the ninth segment are remarkable for the characters of 

 their tips, and seem to be homologous to those that are found on the 

 third segment of Disoma, the fom'th of the ChastopteridEe, and the 

 fifth of Polydora ; the segments behind the ninth are severally provided 

 with two rows of sette on either side ; as to their position on the seg- 

 ments, it is to be noted that those in the anterior portion are found 

 towards the most anterior edge of each segment; but those of the 

 ninth have a more extensive origin ; and behind it the setae gradually 

 pass from the anterior towards the posterior edge of each segment. 



As to the integument, we have to note its high degree of develop- 

 ment in the cephalic and anterior regions, which appears to be corre- 

 lated with the large amount of friction to which the animal is subjected 

 in moving through the sand; and in connection with th;s observation 

 it is interesting to observe that Claparode had noted the delicacy of 

 the integument in sessile annelids. The hypodei*mis is exceedingly 

 well developed. The lateral laraellje consist typically of a delicate 

 cuticular layer investing the hypodermis; at their base there is a 

 bundle of simple setae, but no vessel has been observed to pass to them. 

 In the anterior region the dorsal lamellae are larger and more trans- 

 parent than the ventral. 



In structure the hypodermis is very similar to the integument 

 of the Nemertinea ; it consists of a number of flask-shaped cells or 

 glands, the contents of whicli have the form of clear and of granular 

 spheres ; in the region of the cephulic lobes especially it is jjossible 

 to observe a number of rod-cells, which form a transverse band across 

 the body, behind each row of hook-like setae ; these are also well 

 developed in the caudal region. In the tentacles there are a number 

 of small, but distinctly granulated hypodermal cells. 



The muscular system of the cephalic end of the worm consists 

 of a median and of a lateral pair of longitudinal muscles; the 

 lateral muscles are connected by a chitinous portion, which gives 

 oii' a thin lamella on either side ; the function of this portion is 

 evidently connected with the habitat of the an'mal ; it replaces 

 a circular muscle, and supports the vessels ; while the completeness 

 of the arrangement is spoken to by its connection with the base of 

 the tentacles. In the space on either side of the mouth there is a 

 series of vertical muscular fibres, which have a dorsal origin, and 

 are inserted into the superior margin of the mucous membrane of the 

 mouth, for whicli tissue they appear to serve as retractors. The 

 muscles to the setae are, as a rule, feebly developed, but are very 

 similar to those of allied forms. It is impossible for us to follow the 

 author through all his details, but it may be of interest to point out 



