404 TRANSACTIONS OF SECTION D. 
On Maui, Molokai, and Lanai there are three groups, one red-marked, one 
black and dark-winged, and one with pale bands on some of its species. 
On the largest island, Hawaii, in the S.E., all the groups tend to fuse into 
a single large assemblage of black, dark-winged insects. 
The species form structural groups of which the members, although obviously 
closely related, enter different colour-groups in the various islands. In other 
words, the colour-grouping is entirely independent of zoological affinity. 
2. The Development of Trypanosomes in the Invertebrate Host. 
By Professor Hh. A. Mrncutn, F’.R.S. 
If an analysis and cémparison be made of those instances in which it can be 
claimed that the development of a given species of trypanosome in its invertebrate 
host is known in at least its principal traits, it is seen at once that in every 
such instance there is a part of the developmental cycle which is constant in 
occurrence and uniform in character, and another part which is of inconstant 
occurrence and very variable in character. 
In the constant part of the cycle the parasite always assumes the crithidial 
type of structure and multiplies incessantly in this form to produce a lasting 
stock of the parasite, certain individuals of which change sporadically from the 
crithidial into the trypaniform type and so become the final, propagative form of 
the development, destined to pass back into the vertebrate host and establish the 
infection in it. During hunger-periods the crithidial forms may pass tem- 
porarily, in some cases, into the resting, non-flagellated leishmanial form, until 
food is again abundant, when they form a new flagellum and revert to the 
crithidial type of structure. 
The inconstant part of the cycle, when it occurs, is intercalated at the very 
beginning of the development in the invertebrate, and lasts but a relatively 
short time; it is derived directly from the trypanosomes taken up by the 
invertebrate from the vertebrate host, and takes the form of an active multipli- 
cation of the parasites in either the trypaniform or leishmanial condition. In 
the cases where this early multiplicative phase is wanting altogether, the 
trypanosomes taken up by the invertebrate host pass at once into the crithidial 
phase. 
When a further comparison is made between the development of trypanosomes 
in the invertebrate host and the development of the closely allied species of 
Crithidia and Leptomonas which have no alternation of hosts or generations, 
but are confined during their entire life-history to particular species of inverte- 
brate hosts, it is seen at once that the life-cycles of these parasites of inverte- 
brates are similar in all essential points to the crithidial phases of trypanosomes 
in their invertebrate hosts. It is evident, therefore, that the crithidial phase in 
the development of a trypanosome is to be interpreted as a reversion to, or 
recapitulation of, the type of development that occurred in the ancestral form 
which was originally a parasite of the invertebrate alone, before it had obtained 
a footing in the vertebrate host or had acquired the trypanosome-like type of 
structure ; while the multiplicative phases of variable character preceding the 
crithidial phase in trypanosome-development are to be regarded as having been 
intercalated secondarily into the life-cycle and of no phylogenetic significance. 
3. A Comparison of the Sizes of the Red Cells of some Vertebrates. 
By J. Burton Crevanp, M.D. 
In searching blood-films from Australian birds for parasites, it was noticed 
that the red corpuscles of a heron were distinctly larger than those of the 
various Passerine birds examined. This led to systematic measurements of the 
sizes of the red cells of various Australian vertebrates. The slides examined 
have been all stained by ‘dry’ methods, wet fixation and staining methods 
being impracticable in the field. Experience shows, however, that this method 
may be relied on for the purpose in view. 
