i8 



A-> regards the labial tentacles, Fauroi finds in ('. membranaceus an arrangement which 

 inay be expressed thus: 



2, i. 3, i 2, i, 2, i 2, i,4, 2 i, 3- \, 3, 4, 3, i 2, 4, 1, 2 | 1, 2, 1, 2 .(, 3. 1,2 — 

 while Cari gri n finds 



, 1,3,4 2. 3. 2, 4 3. i.3i 2 >3i 1» 3 4,2,3,2 4,3,1,2—. 

 \'\n Beneden gives an arrangement for C. lloydii which maj \«- expressed by 



2,1,3,4 2.3,1,4 4,2,3,0,3,2,4 4, 1, 3, 2 | 4, 3, 1, 2 — , 

 while Carlgren finds in the same species 



■» 1 ■• i I *> ■» "> 1 2 "» 1 { ) 1 1 1 I 2 2 2 I A 2 T 2 



In (. Carlefren finds the same arrangement as in C. membranaceus. 



In looking over these results it seems clear that there is a general similarity and the 

 diffi ■ are probably largely due to the difficulty of correctly following the lines ofthevarious 



and avoiding the danger of being deceived by differences of contraction. 



In /'. Hmbriatus the arrangement I found to be 



1, 3, 2. 4 | 1. 3, 2. 4 i, 3, 4. 2, 4. 3, 1 4, 2, 3, 1 j 4, 2, 3, 1 -, 

 although it must be said that a distinction between the fourth and third cycles was not always 

 discernible. For the labial tentacles 1 obtained the formula 



> 1 1 a > 1 2 A 2I121I2A212AÏI2 . 



The arrangement of the marginal tentacles is, therefore, identical witli what Carlgren found 

 in C. membranaceus, C. lloydii and C. solitarius, but I find a difference in the arrangement 

 of the labial tentacles, a difference which may. however be due rather to the difficulties ot the 

 determination and to the small number of examples (2) suitable for examination. 



In other forms, however, decided departures from tliis arrangement occur. Thus in C. 

 iaeda the marginal tentacles seem to be arranged in only two cycles, their formula being 



2I2ll2I2I 2 I 2 I 2 I 2 [21 21 2 1.2 



while the labials are on a quadricyclic plan, their formula being 



1.2,4,3 1.2,4,3 1,3,4,2,4,3,1 3.4,2,1(3,4.2,1—. 

 In C. monostichus the marginal tentacles, so far as could be determined, seemed to have the 

 same formula as C. taedus, but, on the other hand, the labials were in a single row. 



In nu larval forms has an arrangement of the ifiitacles in multiple cycles been observed, 



all, both marginal and labial, lying in a single cycle. The multicyclical arrangement of the adult 



may be due to merely mechanica! causes, as was suggested by von Heider. This explanation, 



lic/ by itself hardly sul >r the regularity of the arrangement recurring in the various 



quartette groups, and the possibility of some additional factor imposed by the arrangement of 



mesenteries suggests itself. From what is seen in larval forms it is evident that the formation 



of new mesenteries always precedes that of new tentacles, and, consequently, the tentacles 



ding to any mesentery is that communicating with the intermesenterial chamber nexl 



it. An examination of the marginal tentacles of the quartettes wil! show that the 



proximal cycles are those corresponding to the macrocnemes, while those 



iS 



