vou2.pt. 2.] A TAX0N0MIC STUDY OF THE SALPIDAE METCALF. 41 



lip, differing in this regard from the aggregated Cyclosalpa jloridana. 

 The relations in the older zooids are the same, except that the first 

 sphincters of the dorsal and the' ventral lips are continuous, form- 

 ing one muscle, which has no connection with the oral retractor. 



This divergence in the connection of the admarginal oral sphincters 

 in the younger and older zooids makes one at first doubt the constancy 

 of detail in the arrangement of the muscles in at least the aggregated 

 Salps, but we have as yet no sufficient studies of variation in the 

 Salpidae to determine this matter conclusively. In the aggregated 

 zooids, as in the embryo, there are considerable changes during the 

 process of establishing the adult condition of the muscles, but, once 

 fully developed, these conditions so far as our studies indicate are 

 constant. 



The gut forms a long narrow loop, lying chiefly outside the body 

 proper, in a long protuberance conveniently named by Hitter the 

 post-abdomen. At the point of union of esophagus and intestine 

 arises a long slender caecum, which passes out into a separate slender 

 pouch of the post-abdomen. These relations are best shown in the 

 dextrodorsal view drawn in figure 25, on plate 10. Observe the 

 intestinal gland, opening into the intestine at the point of origin of 

 the caecum and running across the space in the loop of the gut, to 

 branch over the distal portion of the intestine. 



The elongated testis (pi. 10, fig. 25, t.) fills nearly the whole of the 

 larger of the two slender mantle pouches connected with the post- 

 abdomen. Its duct passes over the bend of the intestine and dorsal 

 to its distal end. In the younger zooids we can not trace it beyond 

 this point, but in one of the three larger zooids, which we stained, 

 we could trace a faint line of apparently degenerating duct forward 

 on the right side until it joined the oviduct a little beyond the young 

 embryo. The ovary lies on the right side, in front of the last body 

 muscle, the oviduct extending forward nearly to the third body 

 muscle. 



At the tip of the caecum is an elongated, spindle-shaped group of 

 cells of problematic nature (q in fig. 25, pi. 10). They resemble 

 elaeoblast cells. The heart is in the usual position. Below it, in 

 the younger zooids, is a vesicle subtended by a layer of cells whose 

 appearance again suggests comparison with elaeoblast cells. There 

 is little value in discussing the nature of either group of these elaeo- 

 blast-like cells until their development is known. 



The outline of the aperture of the dorsal tubercle is shown in 

 figure 24, plate 9. 



The ganglion, the neural glands, and the outgrowths from the 

 ganglion, near the glands, resemble these organs in the aggre- 



