265] TURBELLARIA FROM THE MISSISSIPPI BASIN— HIGLEY 71 



accomplish this, however, as the rhabdocoel will either draw up into a com- 

 pact ball hard to take hold of or wiU swim away, scraping off its tormentor 

 in some mass of algae. Many, of course, must meet their death caught in some 

 maze of filament or mass of loose mud, but in open water they seem to be safe 

 and able to swim quickly away from any danger. It may be, of course, that 

 the taste is not delightful to some forms or the presence of dermal rhabdites 

 may make them unfit for food. In some way they seem to be able to live 

 a life singularly free from attack and they mingle in the most courageous man- 

 ner with many species of larger forms, tho for the most part lurking in some 

 secluded part of the deeper water and coming out to the light only occasionally. 



They move very gracefully with but little muscular contraction. The 

 coat of cilia serves as an efficient organ of locomotion and the result is a very 

 even gliding, lacking entirely the twisting and turning so characteristic of other 

 types. In pushing thru small openings or entanglements, there is more or 

 less muscular contraction but otherwise the cilia are able to propel the body 

 unaided. 



In case of slight injury there must be some amount of regeneration pos- 

 sible, but there is little evidence of this. Among thousands of individuals 

 examined, none were found in the process of healing wounds or regenerating 

 lost parts. This fact is conspicuous in comparison with other species where 

 scars and wounds of one sort or another are common. With the above may 

 be correlated the fact that no asexual budding has been discovered. It would 

 appear, also, that a form of such complexity does not possess the power of 

 unlimited regeneration but a condition of entire lack seems improbable. Fur- 

 ther study will doubtless reveal some possibihty along this line. 



Typhlo plana viridata (Abildgaard) 1789 



Figures 22, 27, 30, and 31 



This is another species taken frequently during April and occasionally in 

 the summer and fall. My individuals, although very evidently to be identi- 

 fied with the European form, vary somewhat from that, and also from those 

 specimens hitherto found in this country. 



The animals seem to come entirely from bottom water or from masses 

 of algae living close to the bottom. The size and shape variations are perhaps 

 the most interesting. The exact length is exceedingly constant. More than 

 three-fourths of the individuals measure 0.5 mm. There are differences, how- 

 ever, in the plumpness so that the animals do not appear alike. The other 

 one-foiurth of the individuals seem in comparison, very long and slender, for, 

 while they measure only lOO/x more in length, the relative width is much less. 

 The shape is quite different from other forms. The slope toward the tail is 

 much more gradual altho the tip itself is not sharp; that is, the posterior region 

 is not blunt and stubby, but more slender than is usual. The middle part of 

 the body is round and not so cyUndrical; then, too, it slopes into a sUghtly 

 narrower neck-like portion which again rounds out into the head. This 



