892 SUMMARY OF CURRENT RESEARCHES RELATING TO 



ordinary interest as having to a greater extent than any known larva, 

 characteristics of the young of both the group of Chsetopods and that 

 of the Marine Polyzoa. Of all knov^n worm larvge it has the closest 

 likeness to Mitraria. It is, however, still very far removed from it in 

 many points of structure. The Polyzoan larva which it approaches 

 most closely is djclopelma, the young of Loxosoma. It has many 

 affinities with Oyclopelma as well as with Mitraria, and seems inter- 

 mediate between the two. 



A detailed description with four figures is given, and it is pointed 

 out that it has one highly characteristic Polyzoan feature. The ciliated 

 belt is reflexed over the lower half of the body in the same way that 

 a homologous structure is turned back in Cyclopelma. The spines 

 appended to the posterior region of the body are probably temporary, 

 and are homologous with the embryonic sette in Spio, Prionospio, and 

 several other genera. They approximate nearer the setse of Mitraria 

 as far as position goes, although they are not mounted on any special 

 prominence, and arise from the posterior body region which bears the 

 terminal ciliated prominences. In Mitraria there are no eye-spots 

 similar to those which have been described in the new larva. In the 

 young Loxosoma there are two well-marked ocelli. 



As only a single stage in the development was found, while there 

 is no doubt we have a larval Annelid, it is impossible to say to what 

 family of Ohsetopoda it should be referred. 



Head-Kidney of Polygordius.* — J. Fraipont confirms the greater 

 number of observations of Hatschek on this simple Annelid, and adds 

 to them the results of his studies on a new species, P. neapolitanus. 

 The secretions noted by Hatschek are considerably larger in the new 

 species and resemble drops of fat. When the organ attains its highest 

 degree of development there are ordinarily two infundibula at the 

 extremity of the vertical branch and three at the end of the horizontal 

 branch of the organ. In some larvse a third branch is to be detected, 

 at the end of which there are one or two funnels. There appears to 

 be a considerable amount of variability in the number of the funnels, 

 and, consequently, in the general appearance of the organ. Fraipont 

 finds that the excretory canal is not in direct communication with the 

 body-cavity by the intermediation of the funnel. The radiating sides 

 which support the infundibular membrane are hollow canaliculi 

 which terminate blindly at their free end and open behind into a poly- 

 gonal space which is only in relation with the lumen of the excretory 

 canal. These canaliculi vary greatly in number — from three to six ; 

 they may be straight or curved in various directions. 



The excretory infundibula of the larva of Polygordius do not seem 

 to have any close or real resemblance to those of Kotifers, Trematodes, 

 or Cestodes ; the large excretory canals correspond phylogenetically 

 to the large canals of these forms, the canaliculi which end blindly 

 represent the remnant of the system of canals of the second order 

 which are found in many Rotifers, and in nearly all Platy helminths ; 

 the fine canaliculi of the latter are not found in Kotifers, while the 



* Arch. Biol., v. (1884) pp. 103-10 (1 pi-). 



