86 Part III. — Twenty-third Annual Report 



Additional measurements of lobsters of different stages : — 



Date. 



Stage. 



Measurements. 

 Mm. 



Sept. and Oct. 

 1902. 



?» 



Sept. 1902. 



"IV" Zoea. 

 M. 



+ 1 



1-5: 1-5: 1-6: 1*6. 



1-5: 1-5: 1*5; 1-5: 

 1-6: 1-6. 



1-55: 1-55: 1-6: 1*65: 

 17: 1-7. 



Death of the Young Lobsters, First Young Stage and Later. 



The majority of the young lobsters reared at the Laboratory have died 

 shortly after casting. As a rule, the death took place gradually, as if a 

 disease had seized them immediately on casting. The lobster became at 

 once sluggish, moved about with difficulty, and simply ebbed away. 



October 23rd (No. 3). — One of the young lobsters cast, but became weak 

 immediately after, and was hardly able to move a limb. It was removed 

 to a larger vessel with a good supply of water, and it seemed to be 

 reviving on the 28th. On October 31st it was livelier • it could move 

 its pleopods, but seemed to be paralysed in the thorax ; a faint movement 

 of the antennules was noticed. It had a large swelling on its left side at 

 the hind part of the carapace. It was dead on November 3rd. 



On October 31st (No. 5) a lobster that had not cast recently was seen 

 to be almost dead ; there was just a little movement detected in the last 

 pleopod. On November 3rd it was dead and covered with a fungoid 

 growth. 



On November 3rd (No. 6) a lobster which was half-cast was found as 

 if dead. No movement was noticed. The lobster was torn asunder, and 

 it was then seen that life still remained, as vermiform movements of the 

 organs were detected. A puff of white fluid material was squeezed from 

 the anterior half of the body, and examined by means of the microscope. 

 It was seen to consist of great numbers of infusors of various kinds, the 

 majority being very small and roundish in shape ; others were long, 

 pear-shaped. Some were progressing with an eel-like motion. Sporo- 

 spheres consisting of a mass of minute infusors were made out. The 

 water in which the lobster was had no infusors in it when a drop was 

 examined. 



The death of the young lobsters is, without doubt, due to the rapid 

 development in them of these inf usor parasites. It is possible that during 

 the casting process the infusors may gain admittance to the body, and 

 their rapid multiplication there results in the death of the host in a few 

 days. 



One lobster, the largest reared, measuring 1 inch (2'5cm.) in length, 

 reached that size by a cast on October 31st 1904. On November 3rd it 

 appeared to be dead. On examination a little movement was detected in 

 its limbs. It was removed to a large jar, but did not recover. 



