176 ILLINOIS BIOLOGICAL MONOGRAPHS [464 



he said "In a cod examined on the 15th of March, 1885, two specimens 

 of Bothriocephalus rogosus had severally attained a length of nearly fifteen 

 inches, and their anterior segments for an inch or more downwards, were so 

 firmly impacted within the pancreatic coeca, that it was found impossible 

 to dislodge them without injuring the filamentary head and neck. As if 

 to make the anchorage doubly sure, the cartilaginous thickening of the invaded 

 pancreatic coecum had degenerated into a calcareous and contracted cylinder, 

 twisted upon itseK in various ways." Olsson (1867:54) likewise found a 

 pseudoscolex in this species, which he described as being degenerated m Gadus 

 morrhua to a yellow, elongated mass which disintegrated on contact with 

 water. It was 18 to 25mm. in length by about one-half a millimetre in diame- 

 ter, while its position was, as usual, in the wall of a pyloric appendage of the 

 host. He also figured a young strobila from Gadus aegUfinus, the scolex of 

 which he considered to have been invaginated. In his new genus and species, 

 Abothrium gadi, van Beneden (1871:56) observed the pseudoscolex stating 

 that "lis ont la t^te vers le fond des coecums pyloriques, percent ordinaire- 

 ment les parois et forment, par la gaine, souvent dure et entortUlee comme une 

 tabulaire, une saiUie a la surface de cet organe. " So far as the writer is aware, 

 he gave the first figure of the structure, as it is commonly met with, encased, 

 however, by the walls of the pyloric coecimi in which it was found lodged. 

 Von Linstow (1889:242) described and figured a scolex somewhat similar to 

 that of A. crassum, excepting that the apex was hollowed out to form a six- 

 comered opening which communicated with both bothria. Linton (1890: 

 750) found pseudoscolices in examples from the codfish, "Gadus morrhua," 

 which were much as described by Olsson, since he said that "each of the 

 specimens in this lot has the head and anterior part of the body buried in the 

 pyloric caeca, where they have imdergone degeneration to such an extent that 

 no appearance of bothria remains. Around the parts thus enveloped by the 

 caeca is a yellowish waxy deposit, the degenerated tissue of the caeca. This 

 adventitious tissue invested the worm so closely that it would be absolutely 

 impossible for the parasite to free itself from its host. " The next important 

 reference to the scolex was by Lonnberg (1891:75) who, while accepting van 

 Beneden's new genus, Abothrium, referred the species back to rugosum of 

 Batsch, and described the metamorphosis of the anterior end of the strobiJa 

 into the well-known pseudoscolex, accounting for the various forms, such as 

 figured here. It is noteworthy, however, that he did not state specifically 

 that bothria are present in very young scohces, before this transformation 

 takes place, nor did he give any figures to illustrate the latter. Matz (1892: 

 114) described and figured a typical scolex for a specimen 36cm. long from Lota 

 vulgaris, while Schneider (1903a:9) in delineating a similar structure for the 

 species from the same host, pointed out its great similarity to the scolex of 

 B. proboscideus (=A. crassum). Perhaps of significance in connection with 

 the question of the metamorphosis of the organ is his statement that "Der 

 ganze Scolex kann sich namlich durch verschiedene Contraction seiner Mus- 

 kebi in ein pfeilformiges, oder fast cubisches, oder sogar sichelformiges Gebilde 



