of the Fishery Board for Scotland. 



117 



The pleopod has no exopodite ; it consists of a single-jointed proto- 

 podite and a 2-jointed endopodite. The endopodite is furnished with a 

 great quantity of fine egg-hairs (fig. 27). 



The eggs have very long stalks and are not arranged along the hairs as 

 in Cancer, but the tips of one or of many hairs are inserted into the stalk 

 of the egg ; and they sometimes pass up the stalk for a considerable 

 distance (figs. 28 and 29). In this case, then, there is never more than 

 one egg to each hair, but very often only one egg to a group of hairs. Its 

 position on the extremity of the hair gives occasion to much rotary move- 

 ment of the egg, and through this the stalk becomes tightly twisted like 

 a rope. 



Some of the hairs of this species are setose over the whole of their 

 length, the cilia being long : the extremity of the hair is bare for a 

 greater or shorter distance. The short egg-hairs are setose on the middle 

 of their length (fig. 27). The cilia are longer at the distal end and 

 become less as they are more proximal. This probably prevents the hair 

 entering the egg very far on its piercing the chorion. 



Galathea dispersa. — In this form there does not appear to be more 

 than one egg to each hair; and a group of hairs sometimes enters 

 one-egg stalk. A cluster of eggs is sometimes found on one fascicle 

 of hairs. 



A condition similar to Galathea dispersa is apparently present in 

 Calocaris macandrece. 



Homarus vulgaris. — The pleopod is short and paddle-like. The endo- 

 podite is 2-jointed. The two branches are provided with the usual 

 setose hairs round their margins, and on the posterior or concave surface 

 of the endopodite there are arranged round the margin the egg-hairs. 

 They are not nearly so numerous as the plumose setse. On the exopo- 

 dite at its basal outer corner there is a fascicle of egg-hairs. There are 

 several fascicles of the same on the protopodite and also on the sternum 

 of the abdominal segment. 



The egg-hairs are extremely delicate. The tips only are ciliated, and 

 the cilia are directed forward along the extremity of the hair (fig. 58). 



The eggs are not attached to the distal parts of the endopodite and 

 exopodite. In this form they are attached in two ways — (1) by the usual 

 stalk attachment to the hair, a condition brought about in a way similar 

 to that of Cancer ; (2) eggs are attached to one another by stalks and 

 without the intermediary of an egg-hair, vide figs. 56 and 57. The stalks 

 which these eggs show, and which may be two or three in number, exactly 

 resemble the stalks of the eggs attached to hairs ; they are without doubt 

 formed by the chorion. In no case were two eggs found to be sticking 

 together in the way in which the demersal eggs of a fish, e.g. Cyclopterus 

 lumjjus, stick together. In the latter case the two eggs form at the point 

 where they are glued together a flat common wall. In the lobster, on 

 the other hand, the eggs are all stalked, and the fact that each egg usually 

 has more than one stalk gives some apparent ground for the theory of the 

 cement-covering of the egg. 



Scott* has recently described the spawning of the lobster. The 

 female lay on its back, and the eggs flowed down into the incubatory 

 chamber formed by the flexed abdomen. When the eggs, just after they 

 emerged from the genital openings, were placed in a glass of sea- water 

 and collected into a heap they all became attached one to the other, " and 

 also to the glass. Moreover, the adhesive material only remains soft for 

 a short time, as when the individual eggs were isolated and prevented 

 from adhering to the glass it was found that at the end of half-an-hour 



* Scott, "On the Spawning of the Lobster." Report of the Lancashire Sea-Fisheries 

 Laboratory for 1902. No. xi. Liverpool, 1903, pp. 20 et seq. 



