The foregoing tables (1-5), representing five series, contain the fundamental data.

The plan was to have twelve specimens in each series. In the case of R. esculenta 1904 and also 1909, there are, however, only eleven in each. The absent records were excluded because the percentage of water, which was not calculated until my return home, showed the excluded specimens to be in abnormal condition.

In the case of R. temporaria 1909 sixteen records were made. In general, the grouping of these data is by threes. There are however three exceptions: In R. esculenta 1904, with a total of 11 specimens, there is one group of two (Records 7 and 8) and in R. esculenta 1909, there is one group of two (Records 10 and 11).

In R. temporaria 1909 there is one group of four. In each case this departure from the rule is indicated in the condensed tables (6, 10, 12, 13,) by a bracketed number following the average for body weight.

It will be noted that in the 1904 series, the column under the heading "Body length" is vacant. This measurement was not made in that year, but was made in the specimens collected in 1909.

It represents the length of the frog from the tip of the nose to the tip of the urostyle, the skin over the urostyle having been split in order to expose its cartilaginous tip; the measurement being taken with vernier calipers.

In the previous paper (Donaldson '08) some measurements on preserved material were introduced without correction for the effects of the reagents used. These cases were explicitly noted. It is of interest to state therefore that, in this paper, the data apply to the fresh material only. Indeed all the measurements were made on the material when fresh except in the case of the leg bones of the two 1909 series. In these cases the legs were brought to this country from Europe in 60 per cent alcohol and then the bones were measured.

A long series of control observations on the legs of R. pipiens treated in the same way and for the same time have shown that

this treatment reduces the length of the femur by 0.70 per cent making it 99.30 per cent of the fresh length, the tibia by 0.73 per cent making it 99.27 per cent of the fresh length; the foot (tarsus-pes) by 1.54 per cent making it 98.46 per cent of the fresh length.

These corrections were applied before the data were used in tables 7 and 8.

TABLE 6

Body weight per millimeter of total length. Averages from groups of three

(A) AVERAGE AMOUNT OF BODY WEIGHT FOR EACH MILLIMETER OF TOTAL LENGTH

The general form of the specimens examined is obtained by dividing the body weight by the total length (table 6). The data in this table are given in Chart 1 and show that in the years

CHART I. Showing the average amount of body weight corresponding to each millimeter of the total length.

0

5

ப

20

1904 and 1909, the European frogs were similar in their general form.

The records for R. pipiens are not entered on this chart. They would run a trifle below those for the European species, showing that R. pipiens was more slender in its general build. This character of R. pipiens taken alone would imply a slightly smaller nervous system, but as we know the contrary is the case.

TABLE 7

Percentage of the total length represented by the combined lengths of the leg bones

(B) PERCENTAGE OF TOTAL LENGTH REPRESENTED BY THE COMBINED LENGTHS OF THE LEG BONES

The absolute values of the percentages in this table are on the average less by 3.5 than those given in the previous paper (see Donaldson '08, table 2). This is the result of a change in the technique of measurement. Previously the total length of the frogs was taken when the animals were suspended, and under this condition a certain amount of flexion persisted in the legs. In the present case the frog was measured when stretched out on the table and lying on its ventral surface. By this treatment the amount of flexion was reduced, and the total length thereby slightly increased. This naturally reduced the percentage value of the sum of the lengths of the leg bones, the measurements of which were made in the same way in both cases. The above mentioned change in technique is the only one which has been made.

The point of importance is that the percentages are nearly the same for the three species which are here compared.

(C) THE PROPORTIONAL LENGTHS OF THE SEVERAL LEG BONES These are shown in table 8 in which the 1904 records have been repeated and a complete series of 1909 records added. It will be seen that there is no essential difference between the obser