440 MORGAN. [Vol. V. 



eye spots which are absent in the Echinoderm larva, and the 

 resemblance between the two larvae is only superficial. The 

 presence of apical plate and its muscle band points rather to a 

 relationship of the Tornaria to the Trochophora. There are 

 several similarities between Balanoglossus and Chordata, but 

 the comparisons made are not always on a sound basis. 



There are a few other recent papers of a general interest in 

 this connection which may be briefly mentioned here. Caldwell 

 in 1882 pointed out a relationship between the Brachiopods and 

 Phoronis, and thought that the Polyzoa might be a related but now 

 a degenerate branch. Further, he thought it possible that Sipun- 

 culus and Phascolosoma might be related to the same types, but 

 on the other hand there is the same probability that they may 

 be farther stages in degeneration of segmented forms like Echi- 

 urus. Lankester, in the article " Polyzoa " {Encyclopedia Britan- 

 nica, 1885), gives a most suggestive classification of the same 

 forms. Under the name Padoxonia he includes Sipunculoides, 

 Brachiopods, and Polyzoa, — the last including, 1st, Pterobranchia 

 (Rhabdopleura, Cephalodiscus) ; 2d, Vermiformia (Phoronis) ; 

 3d, Eupolyzoa (true Polyzoa). The interrelation of Rhabdo- 

 pleures, Cephalodiscus, and Phoronis and the true Polyzoa is 

 discussed, and Lankester also points out the resemblance of 

 Polyzoa to the Brachiopods. Harmer, in 1887, in an appendix 

 to Mcintosh's paper on Cephalodiscus Dodecalophns calls atten- 

 tion to the relationship of this animal to Balanoglossus. He 

 believes, therefore, that Cephalodiscus (and possibly also Rhab- 

 dopleura) must be removed from the Polyzoa and placed 

 amongst the Hemi-Chordata. The egg embryology has not 

 been studied, but Harmer studied the development of the buds 

 and finds, as in Balanoglossus, there is present in the youngest 

 stages five body cavities, — a single anterior pouch opening to the 

 exterior by a pair of water pores, — in the collar region a pair 

 of cavities right and left, — and lastly a posterior pair of sacs 

 forming the musculature of the digestive tract. There is a 

 thickened portion of the ectoderm forming the nervous system 

 in the dorsal part of the collar. The reproductive organs are 

 represented by a pair of gonads, lying in the posterior body 

 cavity and opening by a pair of small pores to the exterior. 

 There is also a pair of gill slits opening from the oesophagus to 

 the outside, beneath the opercular folds of the collar. The 



