FREE-LIVING NEMATODES 



483 



Esophagus with a distinct median bulb, and a more or less distinct 

 posterior swelling. Males with bursa. . Tylenclius Baslian. 

 Genus consisting of numerous species, many of them iwrasilit 

 in plants and sometimes highly injurious. Aquatic species are rather 

 uncommon. A single species found parasitic in a marine alsa 

 I nncipally owing to its economic importance the genus has a very 

 extensive literature. 



Representative species. 



/l^ 9 8. __ 13. -81 



V '.i ' 'l.8'/~ 2._ ■ ■ '2 2 



(- : 



7(6) 



Tylenchus dipsaci Kahn 1857. 



8= 2_ ■ "22 '12' I 5 mm '^ ''|^. S[K'cieS is fouod 



parasitic in onion and hya- 

 , — *]■■ • -^1 ••'•'.. Mmm. ^'"^'1 \i\i\h>, and in a num- 

 1' '9 .2. -NU ber of other plants, and is 



very harmful. The spear, h, i, Fig. II, is shot forth hy the musiles. 

 /, and is used to puncture the cells of the h(jst plant. The sjiear is 

 tubular, and the juices of the host are sucked through the siK-ar into 

 the intestine by means of the bulb, c. Often referred to in literature 

 as Tylenchus devaslalrix. 



Habitat: Europe, America, Australia, and probably throughout 

 the temperate regions. 



Fig. 776. Tylenchus dipsaci. Kiihn. 



I, a female; II. head of the same more highly magnified; III. Uil of 

 a male; IV, view from below, of the female sexual oi)cnin)z; \". cross- 

 section of the neck passing through the median sucking-bulb; \ I. front vktw 

 of the penes and their accessory parts; VII, cross-section through the middle of 

 a female, showing how the body-cavity is filled completely by the ovary- (») 

 and the intestine (3). 



a, lip region; b, tip of spear; c, median sucking-bulb; <f, ncr%T-rinK; 

 e, excretory pore; /, muscles for moving the spear forward; /t, ixwtcrwr 

 esophageal swelling; A, excretory' gland; i, hind end of si)car. thrre-bulbrtl: 

 i, loop in ovary; k, right spiculum; /, muscles for ojjcning the vulva; 

 m, the vulva; n, glandular (?) bodies; o, bursa; p. hind end of ovar>-; 

 q, uterus containing spermatozoa and one segmenting egg: r. segmentrnK 

 egg; 5. vagina; /, the vulva or female sexual opening: «, blind end of ixsterio' 

 rudimentary ovarv; v, intestine, showing its cellular structure; ir. cross- 

 section of an egg; x, anus; y, wings of the cuticula; z. cross-section o( the 

 intestine. (After Cobb.) 



Esophagus with only one swelling, corresponding to the median l)ulb i)f 

 Tylenchus. Males without bursa. . . Aphdcnchiis l^Asu^n 



Genus consisting of numerous species, the niajority parasitic in 

 plants, and often highly injurious. Some sjx-cics prthenoKenetk-. 

 This genus closely resembles Tylenchus. frt)m which it is distin- 

 guished by the absence of the bursa on the males, and by the less 

 developed posterior portion of the esophagus. Thi> latter Ls so 

 deteriorated that it cannot be distinguished from the intestine. 

 The oral spear also is usually less strongly deyeloix-d than in 

 Tylenchus, and its posterior extremity is less likely to pn-si-nt 

 bulbous swelhngs. .\s in Tylenchus, so here, some of the spitics 

 are known to revive years after haWng been dried up and con- 

 verted into "dust." In the dirt or dust adhering to seeds and 

 plants they are often transported long distances, -'^•anv «' ln« 

 species, therefore, are now cosraoiJoUtan. Like I yUtuhus, ihii genu* 

 has an extensive literature. 



Representative species. ^ , u o 



Aplielenchns viicrohiimus Cohh 1891. 





' °^ Habitat: Douglas Lake, 

 Michigan. 



Fig. 777. Aphelcnchus microlaimus. 

 a, the lips; b, the spear; r. the nerve-ring; J sucking-bulb; ''J-f"*^^ 

 vote- f ventral gland; g, blind eivl of testicle; h. inloslinc; i. cuticwU or 

 skS ;•; spStozoonf*. right spiculum or penis; /. piece accr^oo' » 

 the spicula; m, anus; n, papiUa; o, terminus. (.Vflcr Ujbb.) 



