STFDTES OX TITE ErTôPAT; Ai^TTTf' TnEMATODES OF .TAPAX. ]]9 



1^1. X\\ . 1i,u's. - v.^ ()); while ill ('(ilicohi/c aiid Mlcrorolijlc rcticnhihi the 

 vitelline loltos nvo distinetly 1ml less coinj^lctely separnted ihnn e:ic]i 

 ..rl.er (I'l. IFF. fiu-. I; IM. XIX. ti-. !»). In Tri^lmuuw (PI. XXf. 

 iiu'. 7) -mkI ('<ilirohilr (i'l. XXI. i\<s. !*) I li:ne ohserNcd -i îliin Ixit 

 ilistineî inenil)r:iiie sMn'ouiidiiiL:' tlie li)l)es; 1)UT in most orliei" i:'enei*:i 

 thev seemed to Ite coiitaiiKMl in mere ea\itie.s of the mesenehvma 

 destitute of niiv liiiinu' memhrane. 



The volk-eells containe(l in rlie lolies pi-esent ditfei"ent asj^eets ae- 

 eordiiii;- îo tIu- stam^es of develo]»menl . 'Jdie I'ipe cells are of 

 \cj'V ditfereiit size'' in ditferent i>'enera; hut ])i'esent uearlv the same 

 asjX'Ct in all. A^'hile in tlie \ ih'llariiim. thev are of \ai"ious f )nns ae- 

 eordiiiL;' to tlie pressure of rhe iieiu'hhouriiio- cells; hnr when freed thev 

 invariahK' assume the form of ti re^'ular s])here. Eaeh cell is ])i'o\ided 

 witli a distinct, refractive uiemhi'ane (of iolei"ahle Thickness in Moiin- 

 cotiilc f/inKic. V\. XA'Tir. fiii'. Ô). and coutains uumei'ous. yellow, re- 

 frinii'ent ^-nnniles. The vesicailar nucleus usu:dlv occu])ies a ceiitral 

 ])osition. Lî'eneralh' staiiis well, and contains a sinii'le nucleolus ; ir 

 sometimes loses irs aftinitv for st-iiiis. hut alwavs >ul)sisrs ro the verv 

 last. The proto])lasm seems mostiv to liave entirelv disaj^penred in 

 the ri]M' cells; l)iU soiin'tiuies it I'onains as a sliu'litK' stainiiiL;' network 

 hetween the \"olk-i:i'anules (IM. XXI. til!'. 7). liesides tlie ripe Volk- 

 Cells alio\'e descrihed, there are. especiallv in tlie ]>ei'iplHM;al ])art of the 

 vitelline lol)es. inteiiselv staitiin«,:' cells of a mucli smallei" size, closelv 

 ])ressed au'ainst one anothei". and with a liomoo-eneous or. in the largei- 

 ones, ;i finely o'ranular protoplasm. The nucleus is clear and vesiculai-, 



1). T append here in the form of a foot-note the results of the measurements of yolk-cells 

 in different species. The fig-ui-es give the diameter, and ai-e in most cases the average of a 

 nnmlier of measurements (not less than five) : Axiiu' hrteroccrca, 0.03 mm. ; Microcoti/h' cawhita, 

 0.03.") mm. : M. n-tinüatd, 0.015 umi. : JUrlidophura fetroihmi.-i, 0.022 mui. : Dicli<l. .sr.v.s>///.s-, 0.028 

 umi. : OnchiH-otiile ■•:j,iiuici>^. Ü.032 mm.: Moiiiinifi/l,' Ijimti,', O.OIHI mui. ; Kjiihili'lla onttn, 0.021 

 mm.- Trixtoiiiuiit lofaiidiiin. 0.01.') mm.: VV. t'olimvinii, 0.011) mm.: I'r. oriih'. O.OIO mm.: 7>. 

 siuKiitiDii, O.OIS mm. ; 



