Collected Papers - Osborn Zoological Society, Yale University Volume 5 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 Excerpt: ...in respect to formation of double animals were made by Balbiani ('91), working with Stentor, who described two monsters, one of which was formed from a posterior 'merozoite' which was again cut longitudinally in the posterior end. Traces of duality were seen after the first division, but these gradually disappeared, leaving two apparently normal animals. A second monster occurred 'spontaneously, ' but in this specimen the double characters were limited chiefly to the peristomes. The same author ('93) obtained by merotomy a series of multiple monsters which arose from the double monsters which are invariably produced by the failure of a 'merozoite' to complete the process of fission. Johnson ('93) described a double monster in Stentor where the duality was limited to the anterior part of the body. All traces of duality disappeared in a few days. Simpson ('01) observed a double Paramecium which had arisen by the failure of an exconjugant to complete fission. Here the two bodies formed one continuous animal which gave off daughter cells from each end for three generations, after which it developed further abnormalities of form and later died. Prowazek ('04) obtained double monsters from fragments of Stentor. The same author ('04 a) observed in degenerating cultures of Stylonychia a certain amount of hyperregeneration. He figured an individual which had two posterior ends while the mouth and cirri had suffered marked reduction. Jennings ('08) described various abnormalities occurring in cultures of Paramecium. In particular he obtained a race with a marked tendency to form chains, due to the failure of individuals to complete the process of fission. Occasionally a double individual pulled apart, producing paramecia with posterior spines which were handed on to t...