G. H. F. Nuttall and D. Keilin 
191 
Nephrocytes of Mallophaya. 
Essentially similar to the peri-oesophageal nephrocytes of Pediculus are 
certain groups of cells described by various authors in Mallophaga. Thus 
Kramer (1869, p. 455) working with Lipeurus jejunus, found, connected with 
the smaller pair of salivary glands, a peculiar complex of about 14 large cells 
grouped in two rows, the cells ‘‘mostly containing two or four nuclei.” These 
cells showed no efferent duct, but, “ because of their constant seat of attachment 
at the end of the gland opposite to where its duct issues,” they were regarded 
by Kramer as necessarily bearing some relation to the salivary secretion. 
Grosse (1885, p. 549) found similar cells to those described by Kramer in 
Nirmus, Trichodectes, Lipeurus versicolor and L. heterographus . The cells were 
not, however, confined to the crop region, but also occurred in other parts 
of the body in groups of 2-6-8 upon the fat body. Grosse argued that since 
the cells are so generally distributed in the insect’s body their salivary function, 
as supposed by Kramer, is doubtful. 
Snodgrass (1899, pp. 167-8) on the other hand, figured and supposed that he 
discerned an efferent duct leading from similar cells in Trichodectes geomydis, 
the duct opening at the junction of the crop and oesophagus. In Eurymetopus, 
Docophorus and Gonoides , the cells are more numerous than in Trichodectes 
and their “ducts” are difficult to see. According to Snodgrass each “cell 
possesses two nuclear-like bodies (one of these may be a hollow space into 
which the duct opens, such spaces being present in salivary cells of insects), and 
they are all closely pressed together so that they assume polygonal shapes.” 
The observations of Snodgrass are not in accord with those of Kramer and 
Grosse, and they appear very doubtful because the nephrocytes are usually 
tangled up with tracheae, nerves, muscle fibres and real salivary ducts, any of 
which Snodgrass may have taken for a “duct” leading from the nephrocytes. 
Nephrocytes of Pediculus and Diptera compared. 
There remains to be considered the distribution of the nephrocytes observed 
in dipterous larvae since they are comparable with those in Pediculus. 
According to Weismann, Kowalevsky, Bruntz and Keilin, the nephro¬ 
cytes in dipterous larvae are distributed in two distinct groups: (a) One group 
occurs in the form of two parallel dorsal cell-chains applied to the sides of the 
heart; these are the pericardial cells in the strict sense. (b) The second group 
of nephrocytes forms a festoon-like chain (“girlandenfbrmiger Zellenstrang ” of 
Weismann) that is always found suspended ventrally between the two salivarv 
glands (see Keilin, 1917, pi. XII, fig. 46 n.v.). It is highly probable that the 
two groups of nephrocytes in dipterous larvae correspond respectively to the 
disseminated nephrocytes (dorsal) and peri-oesophageal nephrocytes of Pedi¬ 
culus, especially since according to Sikora (p. 58) in Haematopinus eurysternus 
the dorsal nephrocytes occupy a pericardial position. 
Fulmek (1909, pp. 56-58, pis. I, II), moreover, has shown that in Mallo¬ 
phaga the pericardial cells are closely aggregated at the sides of the heart. 
