Miscellaneous. 149 



minal appendages are still absent. The ocellus is still present, as 

 in the first Protozoea ; but the character of the antennae lias changed 

 completely. The ear has appeared in the basal joint of the first 

 antennae, and contains diatoms and other foreign bodies. The two- 

 jointed basal portion of the second antennae carries a short pouch, 

 the rudimentary flagellum, and a long scale with plumose hairs and 

 a single spine. 



The palpus has appeared on the mandible. The exopodites of all 

 five pairs of legs are large, and are now, with the swimmerets, the 

 locomotor organs. The endopodites of the fourth and fifth pairs are 

 somewhat less developed than those of the first, second, and third 

 pairs, which now end in chelse. The abdomen carries only one pair 

 of appendages, those of the sixth segment ; but these are now larger, 

 and are used in swimming. 



The tip of the telson is now almost square, with a very slight 

 notch in the middle line. 



After the next moult the chief change consists in the formation 

 of the first five pairs of abdominal appendages. The endopodites 

 are absent ; and the whole appendage is rudimentary, and is not 

 used for locomotion until the next stage. 



After the next moult the animal reaches the Penaus stage. The 

 scale of the antennae becomes broad and triangular ; the tlagelhim is 

 greatly elongated and is divided into twelve joints. The mandibular 

 palpus is greatly enlarged, and covers up the bases of the antennae. 

 The exopodites disappear from all five pairs of legs ; and the abdo- 

 minal appendages are now functional, although the endopodites are 

 still absent. 



This stage is reached by the first Protozoea in about three weeks ; 

 and all the changes have been actually witnessed in isolated captive 



specimens. 



Our boat is too small for work outside during the windy months 

 of June and July ; and as the ripe females do not come into the inlets 

 and sounds, I have not been able to obtain the eggs or the newly 

 hatched young; but this is the less important, as Fritz MiiHer 

 reared his "first Protozoea" from a Navplius, so that we now have 

 the entire metamorphosis from actual observation. — Johns Hopkins 

 University Circulars, November 1882, p. 6, 



On the Growth of the Molluscan Shell. By II. L. Osboun. 



The structure of the molluscan shell has been studied by means 

 of sections of adult shells by Carpenter and others ; and they have 

 found that it presents an outer membranous horny epidermis and an 

 internal stony portion. Such a method could not give any idea 

 of the actual process of shell-formation ; a knowledge of this could 

 be gained only by study of the first steps. To this end edges 

 of the shell were snipped away, and a thin glass circle thrust be- 

 tween the animal and its shell, care being taken to prevent injury 

 to the mantle* After the lapse of twenty-four hours the shell was 



