63 



cellae. The experiment was repeated with the same unfortunate 



result. Attempts wTre made to feed the larvae by adding cultures 



of diatoms and Amphidinium to the water. At the time of 



writing the experiment has been set going a third time. 



The three stages obtained — the Protozoea, and 1st and second 



Zoeae of Williamson * — are represented in figs. 1 to 3 of Fig. II. 



(page 20), and the time taken between the moults when the 



larvae were in these stages is given below for the first two batches 



of material. 



First Batch. 



May 1st (afternoon ... ... Protozoea found, beginning to hatch. 



May 2nd (morning) ... ... A number of protozoeae isolated, only one 



had moulted in the afternoon. 

 May 3rd (afternoon) ... ... Some protozoeae still present, many 



moulted, and now in first zoea stage. 

 May 5th (morning) ... ... About equal numbers of first and second 



zoeae present, no protozoeae found. 



Second Batch. 



May 5th (morning) ... ... Protozoeae isolated. 



May 6th (morning) ... ... A number of protozoeae present. First 



zoea stage chiefly, with a few second 



zoeae. 

 May 7th (morning) ... ... Only one living protozoea found. First 



and second zoea stages in about equal 



numbers. 

 May 8th (morning) ... ... Some first zoeae still present, chiefly 



second zoeae. No protozoeae fomid. 

 May 9th (morning) ... ... Onlj' second zoeae found. 



This makes the length of the first larval stage (protozoea) 

 between twenty and thirt}^ hours, and in one case as long as forty- 

 four hours approximately. The second stage or first Zoea appears 

 to last from forty-eight hours to seventy-two hours (a few longer 

 than this.) 



These observations are strikingly different from Williamson's, 

 He states that the protozoea stage is of very short duration, and 

 that on leaving the egg-capsule the larva casts immediately. 

 He continues, " I have not noticed the Protozoea stage in cases 

 where the larvae have been hatched out in a tank, but it may be 

 got by washing the egg-mass of a female during the time the young 

 are hatching," 



I think that very possibly Williamson's statement as to the 

 very short duration of this stage may be due to the fact that it 



* " 21st Ann Rep of Fish. Bd. for Scotland," p. IS^j. 



