112 EMBRYOLOGY OF THE PODOPHTHALMATA. 



are furnished with a double row of swimmerets between which the 

 ova are securely carried ; and the ova in this tribe are usually 

 attached by very strong ligatures, thus obtaining additional 

 protection. 



We will now briefly consider the ova or spawn of these 

 animals, noting any particular points of interest that present 

 themselves in certain species. 



The usual form is spherical, but there are exceptions to this 

 rule, for the ova of the Crangonidce are oval in shape, whilst those 

 of the FagutidcB are slightly so, but closely approaching the cir- 

 cular form, as also are the eggs of Hojnarus ?narinus. 



The colour is generally golden, pale brown, or of an amber 

 tint ; and it is worthy of remark that the colour of the ova is 

 certainly regulated to some extent by that of the parent Crusta- 

 cean. For example, the ovum of Fortunmus variegaitts, an 

 animal of a pale tawny tint and inhabiting sand-banks, is of a 

 very light straw colour; — that of Xantho florida, an animal of a 

 warm reddish-brown tint, is rich golden; — and that of Carcbnis 

 tncenas^ an animal of a very variable tint, but usually of a brownish 

 green, is precisely similar in colour to the parent. 



There are, however, one or two remarkably striking exceptions 

 to this rule ; the ova, for instance, of Fatidalus ajuiulicornis (the 

 Thames " red shrimp ") are of a brilliant blue-green tint, and 

 those of Fasiphcea swado, an almost ivory-white Crustacean, are 

 of an aqueous colourless appearance. 



The manner in which the eggs are exuded, and arranged in 

 symmetrical groups on the swimmerets, is difficult to ascertain, 

 and as the females of most species retire either to deep water or 

 to hiding-places at this period, very little is known on this point ; 

 but if we remove one of the swimming-feet and a group of ova 

 from the abdominal segments, and examine them under a low 

 power of the microscope, by means of dark-ground illumination, 

 we shall find that the basal joint or coxopodite of the swimmeret 

 supports, as well, a transparent stalk branching out into smaller 

 and still smaller processes ; and at the end of each of these 

 minute stems is fixed an ovum, so that each swimmeret thereby 

 protects one bunch of ova, and supplies the young with oxygen by 



