116 



Part III. — Twenty -second Annual Report 



Sometimes a hair is seen to be fixed in a position in which it is bent 

 double. 



The egg in the condition last described, firmly attached to the hair, is 

 seen on sectioning (figs. 18a and 18b) to have three layers, which are the 

 three layers noticed by Rathke in the egg of Astacus, but this author 

 regarded the outer investment ("Aussere Eihaut") (the chorion) as derived 

 from the "cement." The three layers of the egg-shell are, (1) outermost, 

 the chorion (dir.) ; (2) next the yolk, the delicate vitelline membrane, m. 

 ("Dotterhaut ") ; and between the two a thicker layer which appears to 

 have been formed simply by the solidification of the perivitelline fluid, si., 

 figs. 18a and 18b (" Lederhaut "). This results in gluing the two 

 primary layers together, in that way forming an efficient protecting enve- 

 lope to the egg. 



The Sloughing of the Empty Egg- Capsules. 



A point of some interest is the manner in which the crab gets rid of 

 the empty egg-capsules after the hatching of the brood. This is effected 

 by sloughing off the outer layer (o./., fig. 32) of the wall of the hair along 

 with the attached capsules, fig. 43. The slough of the hair is shown of 

 greater diameter that it ought to be in proportion to the rest of the 

 figure. 



The minute oval corpuscles found in the cavity of the hair probably 

 function in forming a new inner layer of the hair, and in repairing 

 injuries which the hair may receive. 



The Attachment of the Eggs in other Decapod Crustacea. 



A number of species have been examined with a view to determining 

 whether or not the condition of the attached eggs was such as would lead 

 one to infer that the mode observed in the case of Cancer pagurus was a 

 general one or not. 



The spawning of Carcinus mamas was observed, and it will be treated 

 below. In the following species of Brachyura and Anomura the berried 

 females were examined, viz., Maia squinado, Portunus sp., Hyas sp., 

 Stenorhynchus sp., Eupagurus sp., Lithodes maia. In these the condition 

 of the endopodite and the attached eggs was similar to that of Cancer 

 pagurus, and the mode by which the eggs become attached is the same. 



In Maia squinado (4f inches across the greatest breadth of the cara- 

 pace) the spermatheca is very large, and it differs much from that of 

 Cancer. In the latter the solidified remains of the fluid secreted by the 

 spermatheca are got rid of at the next impregnation ; in the former they 

 are retained, and as a fresh secretion of fluid takes place with each 

 impregnation the spermatheca attains enormous dimensions. 



The berried females of certain Galatheidse and Macrura were also 

 examined, and the details will be given below. 



In the Macrura the pleopods differ much from those of the Brachyura. 

 In some cases the exopodites afford attachment to the eggs, while also 

 hairs on the sternum of the abdomen attach to themselves eggs. Both 

 branches are more or less thickly furnished with densely plumose setae 

 which function for swimming. The egg-hairs, usually ciliated in part, 

 are short, and so there are not many eggs on one hair. The eggs are in 

 large measure attached to the protopodite of the pleopod. The conclusion 

 reached with regard to these also was that the attachment of the egg was 

 effected through the piercing of the chorion by the egg-hair. 



Munida rugosa. — The eggs are much larger than those of Gancer. 



