wnnnrs. 



189 



Flf. 16) —J'nhi 

 rr/is IcEiiifata. 



tube; theri' IS n main oi'iitr:il stem ruiiiiiiiLC tliniuuli tlir fnmt lialf of tlic lioily, and 



Ljiving off many latural raniittcatioiis ; at the niidille of llic Ixidy the main stem forks, 



])roducing two branclii's, whit-h run backwards, and give off many secondary branches. 



Where the three main stems unite, s])rings off tlic lonn, muscular proboscis, which is 



an extensive cylinder for seizing and swallowing food. Tlie |inilioscis will swallow 

 everything small enough; in fact, its dcglutixc |iici|k iisities j)ersist even 

 a after the death of the worm; for, sometimis, when anatomical research 



f'''< has destroyed all the tissues of the creature, ihc |iroboscis, being much 



tougher than the rest, still remains intact, and goes on swallowing every- 

 thing it can seize, as if frenzied liy liuugei-. 



There are many jilanarians ha\ ing a liiauched digestive tract, and 

 they are all classed together, under the common a])pellation of Dendro- 

 c(Ela, in oii]iosition to tlie remaining Turbellaria, which have a simple 

 straight tract, and are therefore called llliabdoccela. It has been as- 

 serted by some writers that tliiae are other species with no digestive 

 canal, for which the term ^Vc(ela lias been projiosed. It seems, how- 

 ever, more probable that the authors alluded to have betai careless in 

 their observations anil hasty in tlic^ir conclusions than that there are 

 any planarians really lacking a digcsti\e tract. 



Of the Dendrocoela, one of the commimest is Pob/velis keviffata, of 

 which we give a good figure, liorrowed from Dr. Schmidt's great work 

 ■' "^'^^ on the natural history - , _ 



of the lower animals. 

 Of the Dendroccela, besides the 



three species already mentioned, the 



naturalist distinguishes many others. 



A few are found in moist earth, a 



goodly number in fresh water, but the 



majority are marine. The marine 



forms differ, for the Tnost |)art con- 

 siderably, from the genera above dv- 



scribed. The rej)roductive organs, 



which are quite complicated in all 



Plathelminths, are especially different. 



The body is generally very broad and 



thin, often translucent and beautifully 



colored. In some cases a large size, a 



length of several inches, is attained. 



I>y way of illustration, we can men- 

 tion only a single very beautiful form, 



very common in the Bay of Naples. 



The animal ( Thi/sanozoon) may gro\\- 



to nearly an inch in length. The back 



is covered with many rows of dark 



colored papilla'. On the head end is 



a jiair of ear-sha]ied outgrowths, which 



liroject obli(juely upwards, and a])pear to act as tentacles, with a most sensitive touch. 



The ventral surface is pure white. The artist has represented the animal clinging 



"^^ 



^ 



