94 Miscellaneous 



MISCELLANEOUS. 



On the Body-cavity of the Sedentary Annelids and their Segmental 

 Organs ; with some Remarks on the Genus Phascolosoma. By 

 M. Cosmovici. 



The general body-cavity of the sedentary Annelids is divided into 

 several compartments by diaphragms, which sometimes exist only 

 in a portion of the cephalothoracic region (Arenicolce, Terehelloz, 

 Clymenice), sometimes throughout the length of the body (Serpulkhc) ; 

 and then each segment has a cavity more or less independent of its 

 neighbours. There are also divisions in the opposite direction. In 

 sections there are seen a central cavity filled by the digestive tube, 

 and two lateral ones separated from the former by muscular bands 

 in the form of oblique diaphragms. A communication exists between 

 all the cavities through the interstices of the fibres of the partitions. 

 The lateral cavities contain the feet with their retractor muscles 

 and the segmental organs : these are the pedal cavities. 



In Chcetopterus pergamentaceus the arrangement of the cavities in 

 the three vesicular segments is interesting. The median cavity, 

 containing tho digestive tube and the genital glands, does not com- 

 municate with the lateral cavities, which are occupied by the reno- 

 segmcntal organs, except by the segmental pavilion which opens in 

 the wall of separation. 



In the Clymenios the corpora Bojani are very long ; and at their 

 anterior extremity the segmental organs are attached. After tho 

 eleventh segment there are no longer any renal bodies, and in their 

 place there is a plexus of blood-vessels of remarkable abundance. 

 The position of these networks is such that we may say that they 

 represent so many corpora Bojani formed solely by their vascular 

 framework. 



The ovum of these animals is remarkable for the separation into 

 two parts of the vitelline mass ; one of these, the larger one, is 

 formed of large granules, the other of very small ones. In tho 

 latter is situated the germinal vesicle and the spot, which becomes 

 strongly coloured by picrocarminate. 



Pectinaria belgica exhibits first a pair of very large corpora 

 Bojani, and then two pairs furnished with segmental organs. The 

 genital gland is on the median line, on each sido of the supranervous 

 vessel. The animal is as transparent as glass ; and notwithstanding 

 this the segmental organs cannot be perceived. It is curious that in 

 less transparent animals these organs have nevertheless been 

 observed by translucence and figured. 



With regard to the segmental organs in the Errant Annelides, we 

 find a pair of them in each segment, with a contorted tubo having 

 an internal pavilion and an opening outwards. In the Serpulidaa 

 (a family very rich in genera), among the sedentary forms, the same 

 thing is met with. Lastly, in all the other Sedentaria we find the 

 segmental organs sometimes free, sometimes annexed to the corpora 



