5. Neither should the heat be very great, for the sponge becomes rotten, like plants, wherefore those near the shore are the best, especially if the water is deep near the land, for the temperature is moderated by the depth. When alive, before they are washed, they are black. Their point of attachment is neither single nor dispersed over the whole surface, for there are empty passages between the points of attachment. Something like a membrane is extended over their lower part, and the attachment is by several points; on the upper part are other closed passages, and four or five which are apparent. Wherefore some persons say that these are the organs by which they take their food. 6. There is also another species called aplysia, because it cannot be washed. This has very large passages; but the other parts of the substance are quite compact. When cut open it is more compact and smooth than the sponge, and the whole is like a lung; of all the sponges this one is confessed to have the most sensation, and to be the most enduring. They are plainly seen in the sea near the sponges, for the other sponges are white as the mud settles down upon them, but these are always black. This is the mode of production in sponges and testacea. CHAPTER XV. 1. Among the malacostraca the carabi are impregnated by sexual intercourse, and contain their ova during three months, May, June, and July. They afterwards deposit them upon the hollow part of their folded tail, and their ova grow like worms. The same thing takes place in the malacia and oviparous fish, for their ova always grow. 2. The ova of the carabi are sandy, and divided into eight parts; for a cartilaginous appendage, round which the ova are attached, is united to each of the opercula at their junction with the side; and the whole resembles a bunch of grapes, for every one of the cartilaginous appendages is frequently subdivided, and the divisions are apparent to any one who will separate them, but when first seen they appear to be united. Those ova which are in the centre are larger than those which are contiguous to the perforation, and the last are the least. 3. The smallest ova are as large as millet; the ova are not continuous with the perforation, but in the middle. For two divisions extend on each side, from the tail and from the thorax, and this is also the line of junction for the opercula. The ova, which are placed at the side, cannot be enclosed, unless the extremity of the tail is drawn over them; this, however, covers them like a lid.