Page:Popular Science Monthly Volume 6.djvu/667

Rh corresponding in essential structure with the true legs of the spider. They are jointed or articulated, and capable of considerable movement. Their number and form vary with different genera. In our spider there are three pair, anterior (a), middle (m), and posterior (p). The middle pair are smaller, and ordinarily concealed by the others. Behind the spinners is the median papilla through which opens the vent (v). In front of them is a low, broad, oval-topped papilla (x), in which I find no trace of division into two, nor any silk-tubes. It probably represents the fourth pair of spinners, which exist in the other Ciniflonidæ.

The tips of the spinners are provided with many little tubes, having the appearance seen in Fig. 7. Through these is drawn the gum



secreted by the silk-glands within the abdomen, and all the strands from a single spinner may combine to form a single thread.

It is probable that the different pairs of spinners are supplied from different glands, and that they are employed in making different parts of the net. With the Nephila plumipes, I found that from one pair came only white silk, while another pair produced only yellow. By separating these with pins, soon after leaving the body, and attaching