RHABDITINAE 47 



Hab. Parasitic forms in body-cavity of Beetles and their 

 larvae, either free or encapsuled. Free-living forms in soil, 

 or in material on which the beetles feed. 



Genotype : A. mirabile Leuckart, 1884. 



V. Siebold, 1836, Arch. f. Anat., Physiol, u. wiss. Med., 

 Berlin, 33; Leuckart, 1884, Tagebl. 57 Versamml. deutsch. Nat. 

 u. Aerzte, Magdeburg, 320; 1887, Abh. Math.-Phys. CI. k. 

 Sachs. Ges. Wiss., Leipzig, xiii, 567 ; zur Strassen, 1892, 

 Zeitschr. f. wiss. Zool., liv, 655; Fuchs, 1914, Zool. Jahrb., 

 Syst., xxxviii, 183; Cobb, 1921, Science, liv, 667; Wiilker, 

 1923, Zool. Anz., Ivi, 160. 



The parasitic stages of Allantonema [Filaria] rigida (v. Sie- 

 bold, 1836), which was made by zur Strassen the type of a 

 new genus, Bradynema, seem to agree in aU essential characters 

 with those of A. mirabile. Its free-living stages have not been 

 described, zur Strassen was led to believe that, though the 

 larvae which escaped to the exterior from the host developed 

 into forms of both sexes, only the male forms took any part 

 in the propagation of the race. These, he believed, pene- 

 trated into new hosts and became protandrous hermaphrodites, 

 while the young potential females died, without becoming 

 parasitic or giving birth to any offspring. In A. mirabile, 

 according to Leuckart, there is a definite alternation of genera- 

 tions, the parasitic form, which is the offspring of the fertilized 

 free-living female form, being a protandrous hermaphrodite. 

 On the other hand, Wiilker, as the result of a recent re-study, 

 states that the parasitic form is the female free-living form 

 itself, which is fertilized before penetrating into the host. He 

 believes that the life-history is probably similar in Bradynema, 

 Sphaerularia, Atractonema and Howardula. 



20. Sphaerularia Dufour, 1837. 



Syn. Atractonema Leuckart, 1887, nee Stein, 1878 ; Asconema 

 Leuckart, 1887, nee Askonema Kent, 1870. 



Parasitic form (female) penetrates into host probably imme- 

 diately after fertilization. Here the vaginal region of the 

 ventral surface grows out into a long appendage (finally becom- 

 ing many times as large as the body of the worm), into which 

 pass the uterus and fat-body or modified intestine. The body 

 then becomes an empty sac, and may ultimately become 

 detached. Embryos hatch in utero and escape into body- 

 cavity of host. 



Free-living form. The larva, after leaving the host, lives 

 for several months without taking food. The mouth is com- 

 pletely closed by a stylet-like organ (which, according to 

 Leuckart, is not a true stylet, and which may perhaps represent 

 the buccal capsule). Oesophagus with median and posterior 



