On Stalk-eyed Crustacea. I33 



Cancer i>asurus,vit find that it reaches its final stage when very 

 minute^ f hive frequently taken it, developed, a quarter of an 

 S a^ro s the carapace, and yet this species sometimes 

 attains a weight of 12-lbs., so that the amount of growth that 

 tiles placrduring the zooea form, as compared with the crab 



'ThiiTnTdoubt that these curious Zocea constitute 

 the food of numerous fishes as well as other marine animals 

 Ind that millions upon millions of ^^em are thus destroy d 

 were this not so, the sea bottom could not attord stanain,, 

 7oom to the various Crustacea that would be P-d-ed for 

 Se^umber of eggs deposited by one individual is something 



^'The?i"fems, however, to be a wide difference in the pro- 

 portfonate numbers produced by different species, and it wou d 

 appear as if those species whose young were more especially 

 ffie to this destruction, were more P;ffi<= ^.^-^^^os^ whose 

 young were not so liable owing to their different mode ot 



''poTexamination by the microscope these objects afford a 

 wide and comparatively new field, and apart from the amount 

 S information which they afford to the student of zoology, 

 par Llarly that part of his subject which refers to the embr^^ 

 stages, they are also specially interesting on account of their 

 great beaut^y when shewn by means of dark ground illumina- 

 tion, as also on account of the remarkable structure 01 the 

 developing zooea form of the animals. • .-^^ ;. ;« 



In order to obtain the desired means of examination, it is 

 necessary, with such delicate organisms, to preserve them m 

 such a manner as shall retain their livmg appearance and form 

 and at the same time enable them to be mounted for 

 microscopic examination, not only temporarily, but for tuture 

 Xence^ This it is quite possible to do, but there are a few 

 species the ova of which do certainly lose some of their living 

 Slour. the most notable being that of Pandalus annuhcorn^^. 

 whose eggs are of a remarkable turquoise blue and this colour 

 it is at present impossible, under preservation, to retain 



The method of examination best adapted to this class of 

 object in order to define their structure and make out their 

 general form is by means of the Binocular Microscope with a 

 fi-in. or 2-in. object glass. No. i eye-piece and eithe 

 pirabola or spot-lens ; if, however, the ova be small, or 

 it is desired to examine more minutely he structure of 

 any part, a higher power with different illumination niay 

 b^ resorted to If the objects referred to be thus 

 examined, after proper preparation, they will be found not 

 only to have retained their rotundity and natural appearance, 



