ON THE BEHAVIOR OF TUBICOLOUS ANNELIDS. J7 



cessation. In this process of rapid growth some show a bending 

 while others do not. Again, some bend toward the light, others 

 away from it, and still others continue in the original direction. 

 The point of importance here is not the bending or curving, but 

 Dimply the tube-extension. This extension is not, as I interpret 

 ii , an expression of growth at all, so far as the body mass of the 

 animal is concerned. Seldom are aquarium conditions especially 

 < niidiici\c to physiological growth. What then does such tube- 

 t -xten-ii MI IIH Mil.- 1 Isolated worms lying -ide by side, of essentially 

 similar age, state of vigor, under identical conditions, show the 

 most remarkable differences in relation to tin- matter of so-called 

 gro\\th. < >nr may in the course of a \\eek extend it- tube 3-5 

 mm.; another -hows not the slightest extension of its tube. < >n<- 

 mav extend it- tube in the line of the body axis, /. .. -traight, the 

 oilier -ho\\ .1 -harp curvature from the first. There has been 

 e.jiial access to food, air. liglit. Why ha- not gro\\th been the 

 -ame in direction and amount? As a matter o| laci it may In* 

 doubted \\ lieiher there has been any appiei i.iMe gn>\\ th. Indeed 

 ' mav not these erratic phenomena expre ju-t the oppo-ite, 

 namely, 1m k of growth conditions, or some other ia< tors > onducive 

 to lointcirt.-' And if so then this erratic tube-exten-ion i- but 

 an expn---ioii of such discomfort, an expre ion o| the elloit- 

 iil th. . leatntv to seek better condition-, to n,i< h oiii , as it \\eiv, 

 in -earc h o| i.i.id, air, etc. Indeed, it' my interpretation be cor- 

 rect, the-e ( urvings are but the natural expre i< m- o| eitort- 



at (...id-get tin-^ or respiration adjustments to tho-e particular 



end- in\ol\ed in -nr\i\al or selection. In the light <>l this 

 intei pieiai i"ii the real factors in\o|\e<l in these aspects ot bc- 

 ha\ ior are intrinsic and not cxtrinsit . The lai ter are conditional 

 ami pa--i\ e; the trmer are indi\ idual. acti\ e. causative. 



SPA] I \\/\II. 



Tin- species lit't'ers most markedly from those already con- 

 sidered ill that it possesses a very flexible tube, hence i- capable 

 of considerable range of movement within a region mca-nivd 

 I >v tin- rad in- ot it- own length. It i- a large species at maturity, 

 averaging perhaps about 25 cm. in length, by about I cm. in 

 diameter. In im experiment- care \\.i- taken to ha\e -pccimens 



