ON THE TRYPANOSOME OF THE LITTLE OWL. 
177 
blood of Athene nocfcua belong to one and the same 
species, for which we use the name Trypan os om a noctuae, 
Schaudinn, in spite of the differences between Schaudinn’s 
figures and ours. Above is a scheme showing the connection 
between the different types of individual here described. 
The stout spindles, which are the only forms we have 
found in the summer condition of the trypanosome, and 
which occur, it will be remembered, also in the general 
circulation, are undoubtedly a transmissive phase of the 
parasite; on passing into a mosquito (Culex) they give rise, 
as will be shown in a subsequent memoir, to the develop- 
mental forms characteristic of the Insectan host. It is 
interesting and important to note that an exactly similar 
state of affairs was found to be present in the trypanosome of 
the chaffinch in its summer phase (cf . Case B in the former 
memoir) . 
As indicated in the scheme, these stout spindles arise, we 
feel practically certain, from individuals of the small fusiform 
type, sucli as occurred in the earlier birds, their development 
being along rather a different line from that leading to the 
medium-sized and large “blue” types (the early spring 
phases). Individuals such as that shown in fig. 27 are 
clearly transitional between the small type and the fully- 
developed stout spindle. While the parasite increases in 
length to a certain, but not very great extent, the principal 
direction in which growth or development takes place is a 
pronounced increase in thickness or stoutness of the body 
(cf. figs. 32 and 33 and 40 and 42 respectively, from wet 
films). 
Zupitza (loc. cit.) has, it seems to us, a quite erroneous 
idea about the origin of these stout forms (and, what are the 
same thing, the leaf-like forms). He considers them as being 
later (older) stages of long, slender (so-called “ spirochaeti- 
form ”) parasites. They are regarded as being developed by 
a process of thickening or swelling of the body-protoplasm, 
chiefly in the middle ; concurrently the kinetonucleus is 
pushed further towards the afiagellar end, and the delicate 
