INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY^ ETC. 733 



why the animal, when quiet in a trough filled with sea water, exerts 

 its proboscis every momeut. 



Segmental Organs of the Capitellidae.* — Dr. Hugo Eisig had 

 intended to make a general revision of the segmental organs of the 

 Annelides, but various circumstances, and, more especially, the con- 

 viction that his object would be best attained by making a careful 

 examination of these organs in a ji'i'i'ticular group, have led to the 

 publication of the present essay, which is of interest and of value 

 as bearing on those structures, which the labours of Professor Scraper 

 and of Mr. Balfour have led them to regard as homologous in the 

 Annelides and in the Vertebrata. 



In describing the organs of Notomastus lineatus, the author says 

 that they are typically formed of two processes, of which the longer 

 and broader one leads to the internal, and the shorter and more 

 delicate to the external orifice ; the two orifices are connected by 

 a canal, the cilia of which work outwards; the internal orifice 

 does not, as in most Annelids, float freely in the coelom, but is 

 closely applied to the peritoneal membrane, and is difficult to 

 perceive ; the outer one is, on the contrary, very evident, as it is 

 placed on an elevated infundibular process. The segmental organs 

 are also remarkable for being confined to one segment, where they lie 

 in the groove which separates the dorsal from the longitudinal 

 muscles ; the long axis is ordinarily set parallel to the long axis of 

 the body, and the external orifice is anterior, the looped portion 

 posterior, and the internal orifice median in position. In the adult 

 these organs are confined to the hinder setigerous portion of the body 

 — to the abdomen ; in the younger forms they are found, more or less 

 distinctly, in a number of the more anterior segments, and are 

 arranged in regular pairs, whereas in the adult they may be absent 

 from one or the other side of a segment, or from both sides ; what is 

 more remarkable is that occasionally more than one jjair of organs is 

 to be found in one segment ; but this is still more strikingly seen in 

 Capitella capitafa, where the "segmental organs " are confined to the 

 anterior portion of the abdomen ; in the adults examined they were 

 found in the tenth to the twentieth or twenty-third segments of the 

 body, and each of these segments contained several pairs of segmental 

 organs ; two to three in the more anterior, four to five in the median, 

 and five to six in the most posterior segments ; the organs are here 

 firmly attached to the peritoneal membrane, with the exception of 

 their internal orifices, and so close is this connection that in section 

 the organs appear to be mere thickenings of the membrane ; as to the 

 internal orifices, the number is not always limited to one for each 

 organ. The external orifices are not so easy to find as in Notomastus, 

 inasmuch as they do not open to the exterior, but pass their secretion 

 into the space between the cuticle and the integument proper ; this 

 observation was best confirmed by feeding the annelid with carmine. 

 As a rule, the organs of each segment are distinct from one another, 



* ' Mittb. Zool. Stat. Neapel,' i. (1S7S) p. 93. 

 VOL. II. 8 c 



