136 
MURIEL ROBERTSON. 
the above development. The drying pulls the blepharoplast 
away from the kinetonucleus and makes the thread joining 
them stand out very clearly; it also greatly enlarges the 
apparent size of the blepliaroplast, and very markedly 
increases the flagellar rudiments, which are always thick at 
this stage. In addition to all this these flagellar structures 
stain a deep red corresponding to the chromatic colour. 
That such a stain should be a fruitful source of error is 
obvious. It must, however, in justice be said of this staiu 
that it has done brilliant if unequal service to the advance- 
ment of our knowledge of blood parasites, and has, therefore, 
amply served its purpose. 
The longitudinal division of the kinetonucleus which I 
held to be the first stage in the development of the flagellum 
has been seen again iu resting forms (fig. 1), but iu the light 
of the above observations I do not feel confident as to how 
this appearance should be interpreted. It is iu these, as iu 
the other specimens of Pontobdella previously examined, a 
rai'c appearance, and the evidence for considering this as the 
initial step iu the formation of the flagellum is very much 
less clear in the wet films than iu Giemsa preparations. 
Moreover, I have recently found in T. vittatse that the 
longitudinal division of the kinetonucleus is the ordinary 
method instead of the transverse, as in T. raim; it is, there- 
fore, possible that the point may be open to some variation. 
Division. — The figs. 7, 12 — 17 give pictures of various 
division stages, and it is perhaps in this point that Giemsa’s 
method has, generally speaking, been the least misleading. 
The division starts as a rule by the transverse division of the 
elongated kinetonucleus, but this point is open to slight 
variation. 
The trophonucleus shows first an arranging of the chroma- 
tin in two masses within the karyosome (figs. 7 and 12). A 
well-developed spindle subsequently arises, but the chromatin 
is divided without the formation of an equatorial plate. The 
wet method brings up the spindle very well (figs. 13 — 17). 
Ceutrosomal functions of some kind seem exercised by the 
