888 RECORD OF CURRENT RESEARCHES RELATING TO 



I. linei, on Lineus gesserensis ; and L leptoplance on Leptoplana tremel- 

 laris). 



The relations of the group the author expresses in the following 

 table : — 



Cestoda. 

 Turbcllaria. \ 



I Trematoda. 



Gasterotricha. Protelmintha. Dicyemida. 



I ^1 i 



Orthonectida. 



Gastrseada. 



6. The author discusses the bearing of his discovery upon the 

 gastrula theory, and comes to the conclusion that, although the 

 structure of tbe OrtJwnectida seems to support Eay Lankester's 

 planula theory, or Metschuikoff s parenchymula theory, the primitive 

 form of the Metazoa is the gastrula by invagination. 



Echinodermata. 



New Organs of the Cidaridse.* — Mr. C. Stewart calls attention to 

 the existence in the members of this family of five organs, each 

 borne immediately below the outer extremities of the compasses. In 

 form they are identical with the external branchife of the other 

 families of the Desmosticha, but their walls are more delicate. The 

 author agrees with Miiller in denying the existence of external 

 branchite in the Cidaridae, and believes that the organs described 

 functionally replace them. They are diverticula of the peritoneum- 

 bounded chamber in which the jaws are lodged, and if their function 

 be respiratory, he thinks the chamber must communicate with the 

 surrounding water near the tips of the jaws. These branchias would 

 then have their interior bathed with water, their free surface by the 

 fluid of the body-cavity. It is suggested that the function of the 

 c jmpasses, their muscles and ligaments, is not tbe movement of the 

 jaws, but to vary the capacity of the jaw chamber and so cause a 

 renewal of its water. 



In speaking of the pedicellariae of Dorocidaris -papillata, the 

 frequent occurrence of four-jawed examples of the armed variety on 

 the anal region was pointed out ; also that in all armed pedicellarias 

 of this family which end in a single fang this is hollow, and has an 

 opening on the outer border near the tip ; at its proximal end the 

 hollow opens into the special chamber of the jaw. The resemblance 

 of these to the gemmiform pedicellariae of the Echinidao is indicated. 



The existence of a series of spines projecting from the inner 

 surface of the corona between the inner ambulacral pores is shown in 

 C. tribuloides and Phyllacanthus haculosa ; and also that in D. papillata 

 the amount of spicula development in the genital gland is very 

 variable. 



* ' Traus. Liuu. Soc. (Zool.),' i. (1879) p. 569. 



