348 E. RAY LANKESTEll. 



granular medulla and nucleus. It will be remembered that 

 in Lumbricus, as here, two large forms of Monocystis are 

 noticed — a longitudinal and a spherical (see this Journal, 

 vol. vi). One of the specimens (iig. 3) had two nuclei, a con- 

 dition due either to fission or to conjunction. From so large 

 a Gregarina as this I expected to obtain some information 

 as to minute structure, and accordingly examined the speci- 

 mens with Hartnack's 10 a immersion. There proved to be 

 a Avell-developed cuticle with tubercular markings (fig. 5 and 

 fig, 4 a), a perfectly homogeneous cortical substance, which 

 had a rather yellow colour, and seemed to be very dense, and 

 then a slightly viscous medullary liquid densely crowded, as 

 usual, Avith oval granules. 



I am not able to give a measurement of the tiiickness of 

 the cortical substance ; but it Avas relatively of but very small 

 development, much less in proportion to the diameter of the 

 Gregarina than in the case of Grecjarina (jkjantea. The 

 nucleus in each case Avas perfectly transparent and homo- 

 geneous, and possessed a distinct membranous Avail, Avhich 

 Avas left in a shrunken state on the field, Avhen sufficient 

 pressure Avas applied to burst the vesicle. 



The points to AA^hich I Avould direct attention in this 

 Gregarine are, the sAvimming movement, the tuberculate 

 cuticle, and the homogeneous cortical substance. 



Cysts from various parts of the perivisceral cavity occa- 

 sionally exhibited the Gregarince broken up into the condition 

 of pseudo-naviculse. They are represented in tAvo conditions 

 in the ])late. Like those of Monocijsiis lumhrici, Avhich they 

 closely resemble, the pseudo-naviculae of M. Sipunculi appear 

 at first as spherical corpuscles, subsequently enlarging, and 

 taking on the naviculoid shape. A very coarse-grained pro- 

 toplasmic mass lies Avithin the highly refracti\'e thick Avail of 

 the pseudo-navicula. 



The pseudo-naviculae average about -o-o'Truth of ^^ inch in 

 length; they possess a shred-like filament dependent from 

 one extremity, Avhich is perfectly motionless. 



The existence of such a process is of considerable import- 

 ance, as strengthening the eA'idence in favour of the identity 

 of psorosperms and pseudo-naviculse, since the former are 

 often provided Avith such long motionless processes. A much 

 better marked case of the existence of such a rigid process 

 came before me three years ago, in the course of some ob- 

 servations on Tnhifex ritulormn. A Moiiomjstis is a very 

 frequent parasite in these Avorms, and is to be found in all 

 stages, free and actively moA'ing, conjoined in pairs (Zygo- 

 cystis of Stein), encysted and divided into a greater or less 



