46 SPOLIA ZEYLANICA. 



Out of some hundreds of cysts passed in review under the microscope, 

 Mr. Hornell tells us that he found " in three different instances a 

 miniature reproduction of the parent within the bladder-like 

 posterior division of the body." Mr. Hornell adds : " So far 

 as my observations go only one secondary larva is produced at 

 a time." 



Whilst confirming Mr. Hornell' s discovery, I find that the endo- 

 genously produced larvae, or briefly the endogens, are not so rarely 

 to be seen as might appear from the above quotations from Mr. 

 Hornell's work, but that, on the contrary, most of the individual 

 placunae which I examined contained some of them ; and secondly, 

 I have to add that the multiple formation of endogens mthin a single 

 cyst is a common phenomenon. One of my first preparati ons showed 

 a cyst, 0"38 mm. in diameter, containing numerous (about twenty) 

 endogens, each exhibiting small granules near the posterior end, the 

 larger concretionary granules (calcareous corpuscles) of the parent 

 occurring round aboiit them in the interstices (compare fig. 1). 



The encysted larvse vary much in size, but in general two sizes 

 may be distinguished, a small one less than 0"25 mm. in diameter 

 (becoming greater when turgid with endogens), and a larger one 

 ranging from 0*5 to TO mm. Both forms are capable of producing 

 endogens, and are therefore potential blastogens. For convenience 

 of description and reference it may be useful to refer to the former 

 as microblastogens (in short microgens). and to the latter as macro- 

 blastogens (macrogens). A parent ency.9ted larva bearing one 

 endogen is a phase or " instar," which may be described in one word 

 as a monogen ; with two endogens it becomes a digen ; with three a 

 trigen ; with four a tetragen ; with many a polygen. The utility of 

 this terminology can perhaps only be appreciated by those engaged 

 in practical investigations of a like nature,,but whether this be so or 

 not it happens to suit the occasion. 



A complete cyst consists of an outer adventitious fibrous layer 

 surrounding the parasite, sometimes closely investing it, sometimes 

 with an intervening space which may be occupied by a flocculent 

 substance. A spherical or rounded larva closely surrounded by the 

 fibrous cyst-wall may show in its anterior hemisphere a series of 

 backwardly directed bristles such as may sometimes be observed in 

 the endogens (fig. 4). Another appearance occasionally met with 

 is that of a Avell-defined striated cuticle, the cuticular strise stretching 

 at right angles between the body of the larva and the inner surface 

 of the membrane which is in contact with the fibrous layer. The 

 strife are involved in the constant contractions or swaying movements 

 of the body. I do not know what may be the significance of these 

 different appearances, or whetlier they are connected in any way 

 with the distinction which must exist between the primary and 

 secondary larval generations. 



