The worm inhabits the lung of the frog and toad, and is hermaphrodite (Schneider) or parthenogenetic (Leuckart); the embryos hatched from the eggs find their way through the lungs into the alimentary canal and thence to the exterior; in a few days they develop into a sexual larva, called a Rhabditiform larva, in which the sexes are distinct; the eggs remain within the uterus, and the young when hatched break through its walls and live free in the perivisceral cavity of the mother, devouring the organs of the body until only the outer cuticle is left; this eventually breaks and sets free the young, which are without teeth, and have therefore lost the typical Rhabditis form.
This simple type of life-history has been experimentally proved by Leuckart to be characteristic of Trichocephalus affinis, Oxyuris ambigua and other species.
The adult worm, which is of extremely minute size, the male being only Fi l sth and the female s of an inch in length inhabits the alimentary canal of man and many other carnivorous mammalia; the young bore their way into the tissues and become encysted in the muscles - within the muscle-bundles according to Leuckart, but in the connective tissue between them according to Chatin and others.
Leuckart in 1848 compared medusae in general terms to flattened polyps.
Chun (Hydrozoa ) maintains the older views of Leuckart and Claus, according to which the cormus is to be compared to a floating hydroid colony.
Milne-Edwards removed the Polyzoa; the group was soon further thinned by the exclusion of the Protozoa on the one hand and the Entozoa on the other; while in 1848 Leuckart and Frey clearly distinguished the Coelenterata from the Echinodermata as a separate sub-kingdom, thus condemning the usage by which the term still continued to be applied to these two groups at least.
Leuckart in Graefe and Saemisch's Handbuch d.
Leuckart, Zur Kenntnis des Generationswechsels and der Parthogenesis bei den Insekten (Frankfurt, 1858); N.
(From Korschelt and Heider, after Leuckart.) Peripatus, Diplopoda, Hexapoda and Chilopoda.
(From Parker and Haswell, Text-book of Zoology, after Leuckart.) ll, 19, /' FIG.46.
Their results are best summed up in the three schemes of classification which follow below - those of Rudolph Leuckart (1823-1896), Henri Milne-Edwards (1800-1884), and T.
,ppjv, male, and ToKOS, from Tlktecv, to beget), biological terms proposed by Leuckart and Eduard von Siebold to denote those parthenogenetic females which produce male young, while "thelytokous" and "thelytoky" would denote their producing female young.
- (I) Leuckart, The Parasites of Man (Edinburgh, 1886); (2) Braun, The Animal Parasites of Man (London, 1906); (3) Id., " Cestodes " in Braun's Klassen u.
According to some writers (Leuckart) they are derived from undifferentiated blastomeres, other authorities (Thomas, Biehringer, Heckert) trace them to the parietal cells of the larva.
(X 15 after Leuckart.) B, Distomum macrostomum, showing the digestive and the greater part of the genital apparatus with the cirrus protruded.
Leuckart, Die Parasiten des Menschen (1889- 1894), vol.
MYZOSTOMIDA, a remarkable group of small parasitic worms which live on crinoid echinoderms; they were first discovered by Leuckart in 1827.