484 | _ Mr. L. Doncaster. [Jan. 25, 
these appear to be in cells of a different kind. In the younger larve there 
appear to be cells of two kinds in the developing nervous system, some with 
numerous faint chromatic bodies in the nucleus, and a very small nucleolus, 
which from their appearance and distribution are probably true nerve-cells; 
others, more variable in size, with one or two large conspicuous nucleoli, 
which occur chiefly round the edge of the nervous system or in groups at 
a deeper level. These latter cells resemble the mesoderm cells of the larva, 
and the diploid mitoses appear to occur in them; possibly therefore they 
are immigrant mesoderm cells forming supporting tissue. In female larve, 
of both spring and summer generations, I have found only diploid mitoses 
in the nervous system as elsewhere. 
Abnormal Nuclear Divisions in the Larva. 
In the footnote referred to above, in addition to the haploid divisions in 
the nervous system of the male larva, | mentioned that in larve of both 
sexes giant nuclei occur below the hypodermis, some 15 or 20 w in diameter, 
and that in the single mitosis which I had seen among these nuclei (an 
anaphase, fig. 30) there were at least 50 chromosomes at each pole. 
I have found no further divisions of this kind, and have made no full 
observations on the nature of the nuclei among which it occurs. They 
appear, however, to be in connection with developing muscle-fibres, between 
the hypodermis and the fat-body, and in younger larve they seem clearly to 
be the nuclei of the cells from which muscles are developing. The cells of 
the fat-body have also very large nuclei, which resemble those of the muscle 
cells rather closely, but usually have a less fine and regular distribution of 
the chromatin, Similar nuclei occur in connection with the developing 
muscles of the spring generation, but I have not found any in mitosis. 
Summary. 
The more important observations recorded are as follows :— 
1. There are two kinds of parthenogenetic females in the spring generation 
of Newroterus lenticularis, which lay eggs differing in their behaviour as 
regards maturation. 
2. In the eggs laid by one class of female there is no maturation division ; 
the nucleus comes to the surface, reaches the stage of prophase of division, 
then sinks in for a short distance and divides by a mitotic spindle parallel 
with the egg-margin. In such eggs early segmentation divisions show the 
diploid number (20) of chromosomes, and no polar chromosomes are ever 
found. 
3. In eggs laid by the second class of female the preliminary behaviour 
