REPORT ON THE SCHIZOPODA. 1(35 



Cyrtopia stages, and in the first post-larval stage all of the globules have been fully 

 developed. 



The Internal Organs (PL XXIX.). — As regards the development of the internal 

 organs, the following observation may be here added : — 



The ganglia of the nervous cord are at first imperfectly defined from one another, 

 forming merely a continuous ganglionic mass, exhibiting but slight intumescences at 

 regular intervals. Not till the tail has been fully segmented are the commissures 

 connecting the caudal ganglia distinctly seen, though at first very short. 



The digestive system would not seem to commence performing its functions till after 

 the Metanauplius stage, or when the oral organs have become mobile and armed with 

 bristles and spines, a considerable supply of food-yolk having been left within the body 

 of the Nauplius to be at first absorbed. In the earliest Calyptopis stage, however, the 

 intestinal tube is distinctly seen traversing the wliole length of the body, and, in living 

 specimens, exhibiting energetic peristaltic movements. Anteriorly, at the junction of the 

 intestine with the stomach, a well-marked rounded caecum, also present in the adult 

 animal, is seen protruding above. The liver constitutes at first only two or three simple 

 cseciform appendages on either side {see PL XXIX. fig. 1). These appendages become 

 in the following stages subdivided into short lobes (see fig. 2), which increase gradually in 

 number, forming at length the compound lobular masses constituting this organ in the 

 adult animal (see following figures). The anal opening is found in the early Calyptopis 

 stages at the base of the spathulate extremity of the tail (telson), in the form of a 

 short longitudinal fissure, bounded by two thickened lips (PL XXX. fig. 36). 



The heart, even in the earliest Calyptopis stages (and also in the Metanauplius 

 stage), can be distinctly seen beneath the posterior part of the carapace, and resembles, at 

 least as regards form, in every respect that of the adult animal. In living specimens it 

 may at once be detected by reason of its quick and rhythmical pulsations. Furthermore, 

 the chief arteries would seem to be developed even in these early stages, as shown by 

 Professor Claus in his treatise referred to above (page 149). 



Development of Thysanopoda tricuspidata. Milne-Edwards (PL XXXI. figs. 1-22). 



The development of this form difi"ers in certain points distinctly from that of 

 Nyctiphanes and Euphausia, and the general appearance of the larvae is so very unlike 

 that of the adult animal, that I certainly should not have been able to refer them to the 

 above named form, if there had not, fortunately, been in the Challenger collection a 

 considerable number of specimens in difi"erent stages of development, thus connecting the 

 larval forms with the adult form. The specimen described by Dana as Cyrtopia rostrata 

 I regard as belonging to this species. In the following pages I purpose describing some 

 of the most characteristic stages. 



