. Fresh-water biology. Freshwater biology. PARASITIC FLATWORMS 425 tissue of the host. In some tapeworms the head carries long suck- ing grooves or bothria, and in others round cup-shaped suckers or acetabula. More compUcated hold-fast organs are developed on the scolex in certain groups of cestodes parasitic in marine hosts. A slight constriction behind the head has been given the name of "neck"; many cestodes have no neck. The body usually in- creases in caliber from the head toward the opposite end. The partition lines of proglottids are at first very indistinct, and be- come more
. Fresh-water biology. Freshwater biology. PARASITIC FLATWORMS 425 tissue of the host. In some tapeworms the head carries long suck- ing grooves or bothria, and in others round cup-shaped suckers or acetabula. More compUcated hold-fast organs are developed on the scolex in certain groups of cestodes parasitic in marine hosts. A slight constriction behind the head has been given the name of "neck"; many cestodes have no neck. The body usually in- creases in caliber from the head toward the opposite end. The partition lines of proglottids are at first very indistinct, and be- come more marked as one goes backward along the chain. The form of the proglottids also changes from the scolex toward the other end of the worm. Much has been made of these and other minor details of external appearance in the descrip- tions of cestodes. They are not adequate for the determination of many species and moreover are not of fundamental signifi- cance. Unfortunately very few cestodes are transpar- ent and it is not easy to study the internal struct- ure, since the specimen must first be subjected to a time-consuming technic. Methods for the prepara- tion of cestode material were outlined briefly in the general section of this chap- ter (page 368). Specimens must be kept flat and ex- fprirlprl or fhpv arp rUffirnlf- Ftg. 730. Ophiolaenia filaroides. Mature proglottid, un- lenaea or iney are amiCUlC flattened, showing relationships of organs. Abbreviations toc:^-nrlâ ^r cinrl int/^^rnrpt- r~nr us^d in thisand followingfigures: d, cirrus; a>, cirrus-pouch; SLUUy emu lllucipiCL l,ui de/, vas deferens; ((;, ductus ejaculatorius; e/, vasa efferentia; â 1 em, excretory vessel, ventral; »(, lateral nerve; 00c, oocapt; reCtly. m, ovary; ut, uterus; ra, vagina; vi, vitellaria. X 52- (A£- T-, , 1-1 , ter La Rue.) Each proglottid may be considered as a unit of structure as it contains a complete set of reproductive organs (Fig. 730). With rare exceptions tapeworms. Please no
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
