Mr H. Goodsir on the Sexes of the Cirripeds^ S^c. 101 



preserve them alive for any length of time, and were, there- 

 fore, disappointed in our expectations of seeing them undergo 

 their metamorphoses. We were, therefore, uncertain whether 

 they underwent a first and second metamorphosis, and changed 

 first into the mussel-like form described by Thompson, and 

 then into the parent form, or were simply metamorphosed into 

 the parent form. Seeing that this is a distinct species from 

 that described by Mr Thompson, it is impossible to decide 

 this question until farther observations have been made. 

 Having been fortunate enough, however, in making a series of 

 observations of the same nature on the young of the Balanus 

 balanoideSy which are recorded above, it will now be seen that 

 this question is already decided, viz. that the balani must 

 undergo two changes of form, or perhaps more, before arriving 

 at a state of maturity. 



Wc will now proceed to give a short description of the larva 

 of this species (PI. IV., fig. 11). 



When viewed from above, the body of the animal is found 

 to be pyriform, with the anterior edge rounded, and the pos- 

 terior extremity ending by means of a point. The whole body 

 consists of three segments : the first forms the greater part of 

 the body ; the two last are minute. Two long unarticulated 

 extremities project from the anterior edge on either side of 

 the mesial line, arising, apparently, from the abdominal sur- 

 face of the body. Two short anteimae arise also from this 

 edge, immediately on each side of the above described extre- 

 mities. 



The eye is situated a little behind the anterior edge, and in 

 the mesial line of the body. 



Two very strong thick legs arise from each side of this first 

 segment of the body. These are bipartite, each division aris- 

 ing from a pedicle common to both, which consists of three 

 segments. The divisions themselves are apparently unarti- 

 culated, but are armed with a number of very strong spines. 



The second segment of the body is minute. The third and 

 last is also minute and pointed, and is armed with three strong 

 spines, which are bent to one side (the left side), that nearest 

 the right side being the shortest. 



All of these larvie swim after the manner of the monoculi, 

 by short and sudden jerks. They propel themselves by means 



