She was very firm. She let him infer, if he chose, that he was not indifferent to her; but to none of his instances would she yield her steady conviction that duty forbade her to say ‘Yes’ to his entreaties. He became—small blame to him for being so—almost angry, and tried if reproach would succeed where prayer and argument had failed. In vain. His reproaches brought the tears to Ethel’s eyes, but she never faltered in her resolve.
If he pressed her unduly on this point, she said simply that she must go away. Let him forget her, or learn, as she hoped he would, to regard her as a friend, and then she need not leave High Tor. And then——
And then Lady Alice, Ethel’s pupil, made her appearance, and there was no more opportunity for private conversation; and two days later, Lord Harrogate started for Aldershot.
(To be continued.)
STRANGE SEA ANIMALS.
By the term sea-squirts, the naturalist denominates some of the most remarkable animals which it is his province to study. In more polite phraseology the sea-squirts are termed ‘Ascidians,’ this appellation being derived from the Greek askos, meaning a wine-skin or Eastern leather-bottle, to which, in outward shape and form the sea-squirts bear a very close resemblance. And as a final designation, the animals under discussion may be known as ‘Tunicates,’ since their bodies are inclosed within a tough bag or ‘tunic,’ the chemical composition of which forms, as we shall presently shew, one of the notable points of their structure. The sea-squirts present themselves to the zoologist as a group of beings exhibiting many exceptions to the ordinary rules of animal organisation; and it may also be noted that they have attained a degree of scientific fame almost exceeding that which their most ardent admirers could have expected. The young sea-squirt has thus been credited in certain scientific speculations with presenting the naturalist and mankind at large with a fac-simile of the early progenitor and far-back ancestor of the whole vertebrate group of animals, including man himself—in other words, it is maintained that the young sea-squirt, through some peculiar process of modification and elevation, has given origin to the highest group of living beings. With the promise before us of obtaining information regarding a most interesting group of animals, which are thus held by some savants to possess relations of no ordinary kind to man himself, the reader will require little incentive to follow out the steps of a brief inquiry into their life-history and relations.
The fame of the sea-squirts is by no means of modern date. Aristotle gives us a succinct description of them in his History of Animals under the designation ‘Tethea;’ and by the same name Pliny has made the sea-squirts of classic reputation, since we learn from this latter author that they were included as articles of importance in the pharmacopœia of the Romans. In their commonest phases, the sea-squirts appear as little leathery bags of clear aspect, through the somewhat transparent wall of which the internal organs can be discerned. The resemblance of the animals to the ancient wine-skin has already been remarked. The wine-skin, as every one knows, was made of the stomach of some animal, or of the skin so arranged as to present two orifices or necks. Thus when we look at a common sea-squirt we see a veritable little ‘leather-bottel,’ measuring from half an inch to an inch or more in length, attached by one extremity to the rock at low-water mark, or to the shell we have dredged, and bearing on its upper surface two prominent openings, each supported on a short neck. The origin of the common name of ‘sea-squirt’ is by no means hard to trace. The incautious observer who picks up a sea-squirt which has through unpropitious fate been cast up on the sea-beach after a storm, after a short survey of the sac-like body, may possibly be tempted to squeeze it as a preliminary to further investigation. On being thus irritated, the animal will most likely retaliate by forcibly ejecting jets of water from the two orifices of the ‘bottel;’ this procedure possibly resulting in the relinquishment of the sea-squirt as altogether an unlikely and unfavourable object for further study. But the observation of this unpolite habit on the part of the animal, will be found to assist our further comprehension of its physiology, and of the manner in which the functions of its life are carried on.
A highly curious item of sea-squirt history is furnished at the outset by the consideration of the rough bag or ‘test’ in which its organs are inclosed. When the chemist analyses this part of the animal, he finds it to be composed in greater part of a substance known as cellulose. It so happens that cellulose is a most important constituent of plants, being almost as common in vegetables as starch. Hence zoologists accounted it a strange and unwonted proceeding on the part of an animal, that it should manufacture in a seemingly natural manner a substance proper and peculiar to the plant-world. The multiplication of cases of like kind in animals has destroyed the novelty and unique nature of the sea-squirt’s case; but none the less curious must the fact be accounted, that the animal should mimic the plant in the mode and results of its life. When the tough outer sac is cut open, we come upon a much more delicate and softer structure, known as the mantle. This latter forms an inner lining to the test, and is the structure upon the presence of which the sea-squirt’s power of ejecting water depends. The mantle is a highly muscular layer, and lies next the organs and internal belongings of the animal.
The clearest mode of describing the structure of the sea-squirt is that of beginning with that neck of the bottle-shaped body on which the mouth opens. The mouth leads, curiously enough, not into a throat, but into a large chamber, named the breathing-sac. The walls of this chamber may be simply described as composed of a network of fine blood-vessels; the meshes of this network being provided with those delicate vibratile filaments, named cilia, the function of which is to keep up, by their movements, a constant circulation of the water admitted to the breathing-chamber. Just within the mouth-opening a few small tentacles or feelers exist, these organs serving to guard the entrance to the body. On the floor of the breathing-sac an opening may be perceived; this aperture leading into the throat, and being, therefore, by many naturalists termed the true mouth. And in the way of digestive apparatus, we find the sea-squirt to possess a stomach, intestine, and other organs.