24 ILLINOIS BIOLOGICAL MONOGRAPHS [312 



muscles and under the skin, where L. intestinalis has never been found in birds, 

 so far as the available records indicate. Liihe (1910:18) did not include them 

 in his Hst of hosts for the adult stage of the species. 



Next in order of importance came Donnadieu's (1877) classical experiments 

 in which, after completely reviewing the literature up to date, he conclusively 

 proved that the form found in the body cavities of various bony fishes is the 

 larval stage of that present in the intestines of birds. As a result of his work 

 he combined the two forms under a new name, Dibothrium ligula, confusing 

 at the same time Schistocephalus solidus with Ligula intestinalis. The Hfe- 

 history of the species was later studied by Riehm (1882) by feeding methods. 

 Moniez (1881:37, 81) was the first writer to study the histology of the species, 

 while Kiessling (1882) gave the first description of its general anatomy. As 

 emphasized, however, by Linstow (1901a), Kiessling's work is not very 

 specific, since he ahnost constantly disposed of L. intestinalis by saying that 

 in it conditions were the same as in Schistocephalus solidus. While, apart 

 from Donnadieu and the earlier writers, Willemoes-Suhm (1870:94) was the 

 first to study the development of the embryo v»fith attention to detail, Schauins- 

 land (1885:550) enlarged upon his observations and gave a more or less com- 

 plete description of the process up to the time of the escape of the ciliated larva. 

 Niemiec (1888:2) described the nervous system, andCohn (1898:134) pointed 

 out its resemblance to Sch. solidus in this regard. Zernecke (1895) in the mean- 

 time dealt in his well known work on the finer structure of cestodes with the 

 parenchyma and the nervous and muscular systems in particular; since then 

 little has been done in that connection. The question of segmentation was 

 studied by Luhe (1898). Later the same writer (1899:52) placed the species 

 in his first classification, stating as his belief that there is only one species of 

 Ligula, viz., L. intestinalis (L). The latter conclusion was also arrived at by 

 Linstow (1901a :628), altho he attributed the specific name to Goeze; while in 

 his latest classification Liihe (1910) maintained the same view. 



Consequently, taking for granted in the absence of European material for 

 comparison that the latter has been established as a fact for the European 

 forms, the problem is to determine whether the same species occurs here in 

 America. So far as the majority of specific characters are concerned, one must 

 rely on the descriptions of Kiessling and Linstow (1901a) who seem to have 

 been the only writers to attend to the details of the reproductive system, — 

 and as metioned above, Kiessling's is quite inadequate in this connection. 

 The only American reports of the species are of larval forms: L. monogramma 

 by Leidy (1855:444) and Dibothrium ligula by Linton (1898:438), the former 

 having also listed (1856:46) the doubtful L. reptans. 



Liihe (1910:18) gave the dimesions of the species as 100 to 400 mm. (occasion- 

 ally 1 meter) in length by from 5 to 15mm. in breadth, not distinguishing how- 

 ever, between the larva and the adult in this regard. Linstow (1901 :629) 

 reported a larva from Blicca bjorkna 200mm. long, 9 broad and 3.5 thick, adults 

 from Podiceps cristatiis and Merganser merganser 160mm. long, 4 broad and 1.5 

 thick. Concerning these differences he said that: " Wenn man die Geschlechts- 



