642 PEOPESSOR E. EAY LANKESTER. 



borne in mind, by those who may hereafter have the oppor- 

 tunity of studying Rhabdopleura." 



1. Development of the first polypide of a colony from the 

 egg. What regions of the polypide correspond to the velar 

 (prseoral) area of the trochosphere ? What to its postoral 

 area ? What to its dorsal, what to its ventral surface ? 



2. Is the ovary idiodinic or nephrodinic ? 



3. Are the sexes distinct or united in one individual ? 



4. Do the colonies persist from one year to another ? If so, 

 do the polypides die down and leave only hybernacula and 

 pectocaulus to continue the organism in the next season ? 



5. Do all the polypides develop sexual organs? Is there 

 any special period of bud-production distinct from the period 

 of sexual activity ? 



6. By what method does the young budded polypide make 

 its way through the wall of the axial chamber of the tubarium 

 in which it is at first closely shut ? 



EXPLANATION OF PLATES XXXVII bis, XXXVIIT, 

 XXXIX, XL, and XLI, 



Illustrating Professor Ray Lankester's memoir on " Rhado- 



pleura." 



PLATE XXXVII bin. 



Fig. 1. — Complete colony of Rhabdopleura Norraani, Allman. Drawn 

 from a specimen found growing on the test of Phallusia mammillata at 

 Lervik, Stordoe, Norway. Magnified about three times linear. The test of 

 the Ascidian is represented of a uniform brown tint, the recumbent attached 

 portions of the tubarium of the Rhabdopleura are also shown as brown, the 

 upright polypide tubes are uncoloured. The black line within the tubarium 

 represents the hard stalk (pectocaulus) and other portions of the zoarium, the 

 polypides being all completely retracted, a. Growing ends of branches of 

 the tubarium. b. The oldest portion of the tubarium. c (in Fig. 2). Bifur- 

 cation of a growing branch, d. Completed branches terminating in an upright 

 polypide tube. 



Fig. 2. — A similar colony more richly branched. 



