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The present author gives a definition of paratenic parasitism, and discusses some French, Russian and Polish terms which have hitherto been accepted for determining this form of parasitism. The term proposed by Bear (1952) is considered to be most convenient. The fenomenon of paratenic parasitism has been illustrated by examples of development of some heteroxenous (e. g. Alaria sp., Dipnyllobothrium sp., Spirocerca lupi ) and monoxenous parasites (Toxocara canis, Syngamus traches). It appears frequently to be not an easy matter to distinguish an paratenous host from the conditional intermediate host. It is considered that the latent helmmthoses leading to an inhibition of growth and development of parasites, conneted with the influence of the immune response of the host as well as of the seasons and specific intra-population relationships, are related fenomena to the paratenic parasitism. The author shows a practically considerable importance of the paratenic parasitism, and discusses its value from the theoretical point of view. The discussion deals particularly with the question of the orgin of the fenomenon considered. Is it original or secondary one? Evidence from many sources leads to the conclusion that the paratenic parasitism occuring among the tapeworms and some Nematodes seems to be one the ways leading to the heteroxeny. However, this fenomenon observed among some Nematodes evidences for a disappearance of the parasitism in the intermediate host.
A diagnosis of Wardoides and description of an interesting maturation system of W. nyrocae are given: 14-18 hooks of „coronulus" type, 4 unarmed acetabulum; pseudoscolex behind the cervix; 3 nuclei, type VIII or X, in linear or triangle arrangement; the bottom of the sexual simus is provided with fine spina: cylindric, armed cirrus; trilobular ovary; reticular uterus; oval eggs with external membrane corvered by thick hair; sexual tracts run dorsally in relation to the longitudinal excretory paths. The same individual never shows the coincidence of the nucleus and mature uterus. About 1/3 of the pupulation is composed exclusively of males, 1/3 of hermaphrodites and 1/3 of females. An interesting maturation system, involving in turn the whole individuals or a tendency to sexual divisibility, is assumed.
A reexamination of the type material of Sobolevicanthus terraereginae and a morphological study of new material collected from the same host, revealed earlier unknown features: scolex armed with eight skrjabinoid rostellar hooks 95-122 µm (mean 112) long, the penis-like, unarmed, retractile copulatory part of vagina, armed cirrus, cirrus stylet, protrusible accessory sac with its glands, three genital pores which open independently (two male and one female) without a common genital atrium, and numerous longitudinal muscles of the internal and external layers.
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