Ruedemann-^-Sessile Conularia. 



717 



The general conclusions which can be inferred from the preceding 

 observations are the following : 



1. The smallest shells are often found aggregated in grape-like bunches 

 and are already attached. 



2. The youngest observable stage consists of basal appendage and 

 living chamber. 



3„ The basal appendage reaches about half the size of the living 

 chamber and is stouter and more resistible than the latter. The relative size 

 and strength of the two parts suggests, not only the question after their 

 relative age, but also the possibility that the basal appendage was the 

 preceding one of the two. Though this problem can only be solved 

 conclusively by the finding of still younger shells, it may be permissible to 

 point out some facts which would seem to support the supposition of the 

 earlier appearance of the basal appendage. Its relatively great size and 

 thickness in the youngest stage have already been mentioned. But it is soon 

 outgrown by the living chamber, for while it begins with a length of .3 nun. 

 (cf. PI. IV, fig. 4), it reaches only 4 mm. in the largest cup observed, which was 

 found in a detached state, and none were found in connection with the shell 

 broader than 2 mm. The living chamber, on the other hand, grew from a 

 length of .3 mm. to one of 14 cm. and perhaps still more. As it is obvious 

 that the basal appendage began relatively large but did in no way keep up in 

 growth with the living chamber, it is probable that it was an organ of 

 importance only in the youth of Conularia gracilis. Moreover, as it appears 

 to be in the later stages so strangely out of proportion to the size and 

 supposed weight of the animal and as it is absent in all known adults of the 

 various forms of Conularia, it may have been dropped entirely at adult 

 age. Perhaps it was the first hard 'tegument appearing on the embryo, and 

 the suggestion of A. E. Verrill* that the appendage is "the initial secretion of 

 the shell gland of the veliger-like young" seems to be not inappropriate. 

 It should, however, be remembered that the appendage also grows and does 

 not remain stationary as do the embryonic chambers of the Cephaloj ><></<, to 

 which one might feel inclined to compare it. 



As the general trend of development is from sessile to slow ly moving 

 and from these to faster moving animals, it seems reasonable to regard the 

 presence of the appendage in youth as a true palingenetic character indicating 

 the derivation of Conularia from sessile forms. 



* American Journal of Science, Vol II, July, 1896, p. 80. 



